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Chapter 6

Fractions — Exercise 6(D)

Class - 6 Concise Mathematics Selina



Exercise 6(D)

Question 1(i)

Simplify:

37×25\dfrac{3}{7} \times \dfrac{2}{5}

Answer

Solving,

37×25=3×27×5=635\Rightarrow \dfrac{3}{7} \times \dfrac{2}{5} \\[1em] = \dfrac{3 \times 2}{7 \times 5} \\[1em] = \dfrac{6}{35}

Hence, 37×25=635\dfrac{3}{7} \times \dfrac{2}{5} = \dfrac{6}{35}.

Question 1(ii)

Simplify:

49×35\dfrac{4}{9} \times \dfrac{3}{5}

Answer

49×35\dfrac{4}{9} \times \dfrac{3}{5}

49×35=4×39×5=1245=415.\Rightarrow \dfrac{4}{9} \times \dfrac{3}{5} = \dfrac{4 \times 3}{9 \times 5} \\[1em] = \dfrac{12}{45} \\[1em] = \dfrac{4}{15}.

Hence, 49×35=415\dfrac{4}{9} \times \dfrac{3}{5} = \dfrac{4}{15}.

Question 1(iii)

Simplify:

512\dfrac{5}{12} × 8

Answer

512×8\dfrac{5}{12} \times 8

512×8=5×812=4012=103=313.\Rightarrow \dfrac{5}{12} \times 8 = \dfrac{5 \times 8}{12} \\[1em] = \dfrac{40}{12} \\[1em] = \dfrac{10}{3} \\[1em] = 3\dfrac{1}{3}.

Hence, 512×8=313\dfrac{5}{12} \times 8 = 3\dfrac{1}{3}.

Question 1(iv)

Simplify:

76 of 314\dfrac{7}{6} \text{ of } \dfrac{3}{14}

Answer

76 of 314\dfrac{7}{6} \text{ of } \dfrac{3}{14}

76 of 314=76×314=7×36×14=2184=14.\Rightarrow \dfrac{7}{6} \text{ of } \dfrac{3}{14} = \dfrac{7}{6} \times \dfrac{3}{14} \\[1em] = \dfrac{7 \times 3}{6 \times 14} \\[1em] = \dfrac{21}{84} \\[1em] = \dfrac{1}{4}.

Hence, 76 of 314=14\dfrac{7}{6} \text{ of } \dfrac{3}{14} = \dfrac{1}{4}.

Question 1(v)

Simplify:

338×3673\dfrac{3}{8} \times 3\dfrac{6}{7}

Answer

338×3673\dfrac{3}{8} \times 3\dfrac{6}{7}

338×367=278×277=27×278×7=72956=13156.\Rightarrow 3\dfrac{3}{8} \times 3\dfrac{6}{7} = \dfrac{27}{8} \times \dfrac{27}{7} \\[1em] = \dfrac{27 \times 27}{8 \times 7} \\[1em] = \dfrac{729}{56} \\[1em] = 13\dfrac{1}{56}.

Hence, 338×367=131563\dfrac{3}{8} \times 3\dfrac{6}{7} = 13\dfrac{1}{56}.

Question 1(vi)

Simplify:

12 of 13×34\dfrac{1}{2} \text{ of } \dfrac{1}{3} \times \dfrac{3}{4}

Answer

12 of 13×34\dfrac{1}{2} \text{ of } \dfrac{1}{3} \times \dfrac{3}{4}

12 of 13×34=16×34=324=18.\Rightarrow \dfrac{1}{2} \text{ of } \dfrac{1}{3} \times \dfrac{3}{4} = \dfrac{1}{6} \times \dfrac{3}{4} \\[1em] = \dfrac{3}{24} \\[1em] = \dfrac{1}{8}.

Hence, 12 of 13×34=18\dfrac{1}{2} \text{ of } \dfrac{1}{3} \times \dfrac{3}{4} = \dfrac{1}{8}.

Question 1(vii)

Simplify:

37×59×415\dfrac{3}{7} \times \dfrac{5}{9} \times 4\dfrac{1}{5}

Answer

37×59×415\dfrac{3}{7} \times \dfrac{5}{9} \times 4\dfrac{1}{5}

37×59×415=37×59×215=3×5×217×9×5=315315=1.\Rightarrow \dfrac{3}{7} \times \dfrac{5}{9} \times 4\dfrac{1}{5} = \dfrac{3}{7} \times \dfrac{5}{9} \times \dfrac{21}{5} \\[1em] = \dfrac{3 \times 5 \times 21}{7 \times 9 \times 5} \\[1em] = \dfrac{315}{315} \\[1em] = 1.

Hence, 37×59×415=1\dfrac{3}{7} \times \dfrac{5}{9} \times 4\dfrac{1}{5} = 1.

Question 1(viii)

Simplify:

113×127 of 1141\dfrac{1}{3} \times 1\dfrac{2}{7} \text{ of } 1\dfrac{1}{4}

Answer

113×127 of 1141\dfrac{1}{3} \times 1\dfrac{2}{7} \text{ of } 1\dfrac{1}{4}

113×127 of 114=43×97×54=4×9×53×7×4=18084=157=217.\Rightarrow 1\dfrac{1}{3} \times 1\dfrac{2}{7} \text{ of } 1\dfrac{1}{4} = \dfrac{4}{3} \times \dfrac{9}{7} \times \dfrac{5}{4} \\[1em] = \dfrac{4 \times 9 \times 5}{3 \times 7 \times 4} \\[1em] = \dfrac{180}{84} \\[1em] = \dfrac{15}{7} \\[1em] = 2\dfrac{1}{7}.

Hence, 113×127 of 114=2171\dfrac{1}{3} \times 1\dfrac{2}{7} \text{ of } 1\dfrac{1}{4} = 2\dfrac{1}{7}.

Question 2(i)

Simplify:

23÷115\dfrac{2}{3} \div 1\dfrac{1}{5}

Answer

23÷115\dfrac{2}{3} \div 1\dfrac{1}{5}

23÷115=23÷65=23×56=1018=59.\Rightarrow \dfrac{2}{3} \div 1\dfrac{1}{5} = \dfrac{2}{3} \div \dfrac{6}{5} \\[1em] = \dfrac{2}{3} \times \dfrac{5}{6} \\[1em] = \dfrac{10}{18} \\[1em] = \dfrac{5}{9}.

Hence, 23÷115=59\dfrac{2}{3} \div 1\dfrac{1}{5} = \dfrac{5}{9}.

Question 2(ii)

Simplify:

412÷494\dfrac{1}{2} \div \dfrac{4}{9}

Answer

412÷494\dfrac{1}{2} \div \dfrac{4}{9}

412÷49=92÷49=92×94=818=1018.\Rightarrow 4\dfrac{1}{2} \div \dfrac{4}{9} = \dfrac{9}{2} \div \dfrac{4}{9} \\[1em] = \dfrac{9}{2} \times \dfrac{9}{4} \\[1em] = \dfrac{81}{8} \\[1em] = 10\dfrac{1}{8}.

Hence, 412÷49=10184\dfrac{1}{2} \div \dfrac{4}{9} = 10\dfrac{1}{8}.

Question 2(iii)

Simplify:

1 ÷ 25\dfrac{2}{5}

Answer

1 ÷ 25\dfrac{2}{5}

1÷25=1×52=52=212.\Rightarrow 1 \div \dfrac{2}{5} = 1 \times \dfrac{5}{2} \\[1em] = \dfrac{5}{2} \\[1em] = 2\dfrac{1}{2}.

Hence, 1÷25=2121 \div \dfrac{2}{5} = 2\dfrac{1}{2}.

Question 2(iv)

Simplify:

49÷49\dfrac{4}{9} \div \dfrac{4}{9}

Answer

49÷49\dfrac{4}{9} \div \dfrac{4}{9}

49÷49=49×94=1.\Rightarrow \dfrac{4}{9} \div \dfrac{4}{9} = \dfrac{4}{9} \times \dfrac{9}{4} \\[1em] = 1.

Hence, 49÷49=1\dfrac{4}{9} \div \dfrac{4}{9} = 1.

Question 2(v)

Simplify:

213÷1342\dfrac{1}{3} \div 1\dfrac{3}{4}

Answer

213÷1342\dfrac{1}{3} \div 1\dfrac{3}{4}

213÷134=73÷74=73×47=43=113.\Rightarrow 2\dfrac{1}{3} \div 1\dfrac{3}{4} = \dfrac{7}{3} \div \dfrac{7}{4} \\[1em] = \dfrac{7}{3} \times \dfrac{4}{7} \\[1em] = \dfrac{4}{3} \\[1em] = 1\dfrac{1}{3}.

Hence, 213÷134=1132\dfrac{1}{3} \div 1\dfrac{3}{4} = 1\dfrac{1}{3}.

Question 3(i)

Simplify:

14 of 227÷35\dfrac{1}{4} \text{ of } 2\dfrac{2}{7} \div \dfrac{3}{5}

Answer

14 of 227÷35\dfrac{1}{4} \text{ of } 2\dfrac{2}{7} \div \dfrac{3}{5}

14 of 227÷35=14×167÷35=47÷35=47×53=2021.\Rightarrow \dfrac{1}{4} \text{ of } 2\dfrac{2}{7} \div \dfrac{3}{5} = \dfrac{1}{4} \times \dfrac{16}{7} \div \dfrac{3}{5} \\[1em] = \dfrac{4}{7} \div \dfrac{3}{5} \\[1em] = \dfrac{4}{7} \times \dfrac{5}{3} \\[1em] = \dfrac{20}{21}.

Hence, 14 of 227÷35=2021\dfrac{1}{4} \text{ of } 2\dfrac{2}{7} \div \dfrac{3}{5} = \dfrac{20}{21}.

Question 3(ii)

Simplify:

114×12÷1131\dfrac{1}{4} \times \dfrac{1}{2} \div 1\dfrac{1}{3}

Answer

114×12÷1131\dfrac{1}{4} \times \dfrac{1}{2} \div 1\dfrac{1}{3}

114×12÷113=54×12÷43=58÷43=58×34=1532.\Rightarrow 1\dfrac{1}{4} \times \dfrac{1}{2} \div 1\dfrac{1}{3} = \dfrac{5}{4} \times \dfrac{1}{2} \div \dfrac{4}{3} \\[1em] = \dfrac{5}{8} \div \dfrac{4}{3} \\[1em] = \dfrac{5}{8} \times \dfrac{3}{4} \\[1em] = \dfrac{15}{32}.

Hence, 114×12÷113=15321\dfrac{1}{4} \times \dfrac{1}{2} \div 1\dfrac{1}{3} = \dfrac{15}{32}.

Question 3(iii)

Simplify:

617×0×5386\dfrac{1}{7} \times 0 \times 5\dfrac{3}{8}

Answer

617×0×5386\dfrac{1}{7} \times 0 \times 5\dfrac{3}{8}

Any number multiplied by 0 is 0.

617×0×538=0.\Rightarrow 6\dfrac{1}{7} \times 0 \times 5\dfrac{3}{8} = 0.

Hence, 617×0×538=06\dfrac{1}{7} \times 0 \times 5\dfrac{3}{8} = 0.

Question 3(iv)

Simplify:

34×113÷37 of 258\dfrac{3}{4} \times 1\dfrac{1}{3} \div \dfrac{3}{7} \text{ of } 2\dfrac{5}{8}

Answer

34×113÷37 of 258\dfrac{3}{4} \times 1\dfrac{1}{3} \div \dfrac{3}{7} \text{ of } 2\dfrac{5}{8}

Solving 'of' first,

37 of 258=37×218=9834×113÷98=34×43÷98=1÷98=1×89=89.\Rightarrow \dfrac{3}{7} \text{ of } 2\dfrac{5}{8} = \dfrac{3}{7} \times \dfrac{21}{8} = \dfrac{9}{8}\\[1em] \Rightarrow \dfrac{3}{4} \times 1\dfrac{1}{3} \div \dfrac{9}{8} = \dfrac{3}{4} \times \dfrac{4}{3} \div \dfrac{9}{8} \\[1em] = 1 \div \dfrac{9}{8} \\[1em] = 1 \times \dfrac{8}{9} \\[1em] = \dfrac{8}{9}.

Hence, 34×113÷37 of 258=89\dfrac{3}{4} \times 1\dfrac{1}{3} \div \dfrac{3}{7} \text{ of } 2\dfrac{5}{8} = \dfrac{8}{9}.

Question 3(v)

Simplify:

214÷27 of 113×232\dfrac{1}{4} \div \dfrac{2}{7} \text{ of } 1\dfrac{1}{3} \times \dfrac{2}{3}

Answer

214÷27 of 113×232\dfrac{1}{4} \div \dfrac{2}{7} \text{ of } 1\dfrac{1}{3} \times \dfrac{2}{3}

Solving 'of' first,

27 of 113=27×43=821214÷821×23=94÷821×23=94×218×23=9×21×24×8×3=37896=6316=31516.\Rightarrow \dfrac{2}{7} \text{ of } 1\dfrac{1}{3} = \dfrac{2}{7} \times \dfrac{4}{3} = \dfrac{8}{21}\\[1em] \Rightarrow 2\dfrac{1}{4} \div \dfrac{8}{21} \times \dfrac{2}{3} = \dfrac{9}{4} \div \dfrac{8}{21} \times \dfrac{2}{3} \\[1em] = \dfrac{9}{4} \times \dfrac{21}{8} \times \dfrac{2}{3} \\[1em] = \dfrac{9 \times 21 \times 2}{4 \times 8 \times 3} \\[1em] = \dfrac{378}{96} \\[1em] = \dfrac{63}{16} \\[1em] = 3\dfrac{15}{16}.

Hence, 214÷27 of 113×23=315162\dfrac{1}{4} \div \dfrac{2}{7} \text{ of } 1\dfrac{1}{3} \times \dfrac{2}{3} = 3\dfrac{15}{16}.

Question 4(i)

Simplify:

5(8113311)5 - \left(\dfrac{8}{11} - 3\dfrac{3}{11}\right)

Answer

Using BODMAS we simplify bracket first.

5(8113311)5 - \left(\dfrac{8}{11} - 3\dfrac{3}{11}\right)

5(8113611)=5(83611)=5(2811)=5+2811=5511+2811=8311=7611.\Rightarrow 5 - \left(\dfrac{8}{11} - \dfrac{36}{11}\right) = 5 - \left(\dfrac{8 - 36}{11}\right) \\[1em] = 5 - \left(\dfrac{-28}{11}\right) \\[1em] = 5 + \dfrac{28}{11} \\[1em] = \dfrac{55}{11} + \dfrac{28}{11} \\[1em] = \dfrac{83}{11} \\[1em] = 7\dfrac{6}{11}.

Hence, 5(8113311)=76115 - \left(\dfrac{8}{11} - 3\dfrac{3}{11}\right) = 7\dfrac{6}{11}.

Question 4(ii)

Simplify:

12÷(7835)\dfrac{1}{2} \div \left(\dfrac{7}{8} - \dfrac{3}{5}\right)

Answer

Using BODMAS we simplify bracket first.

12÷(7835)\dfrac{1}{2} \div \left(\dfrac{7}{8} - \dfrac{3}{5}\right)

12÷(7835)=12÷(35402440)=12÷1140=12×4011=2011=1911.\Rightarrow \dfrac{1}{2} \div \left(\dfrac{7}{8} - \dfrac{3}{5}\right) = \dfrac{1}{2} \div \left(\dfrac{35}{40} - \dfrac{24}{40}\right) \\[1em] = \dfrac{1}{2} \div \dfrac{11}{40} \\[1em] = \dfrac{1}{2} \times \dfrac{40}{11} \\[1em] = \dfrac{20}{11} \\[1em] = 1\dfrac{9}{11}.

Hence, 12÷(7835)=1911\dfrac{1}{2} \div \left(\dfrac{7}{8} - \dfrac{3}{5}\right) = 1\dfrac{9}{11}.

Question 4(iii)

Simplify:

213÷(512+334)2\dfrac{1}{3} \div \left(5\dfrac{1}{2} + 3\dfrac{3}{4}\right)

Answer

Using BODMAS we simplify bracket first.

213÷(512+334)2\dfrac{1}{3} \div \left(5\dfrac{1}{2} + 3\dfrac{3}{4}\right)

213÷(112+154)=73÷(224+154)=73÷374=73×437=28111.\Rightarrow 2\dfrac{1}{3} \div \left(\dfrac{11}{2} + \dfrac{15}{4}\right) = \dfrac{7}{3} \div \left(\dfrac{22}{4} + \dfrac{15}{4}\right) \\[1em] = \dfrac{7}{3} \div \dfrac{37}{4} \\[1em] = \dfrac{7}{3} \times \dfrac{4}{37} \\[1em] = \dfrac{28}{111}.

Hence, 213÷(512+334)=281112\dfrac{1}{3} \div \left(5\dfrac{1}{2} + 3\dfrac{3}{4}\right) = \dfrac{28}{111}.

Question 4(iv)

Simplify:

(378335)÷12\left(3\dfrac{7}{8} - 3\dfrac{3}{5}\right) \div \dfrac{1}{2}

Answer

Using BODMAS we simplify bracket first.

(378335)÷12\left(3\dfrac{7}{8} - 3\dfrac{3}{5}\right) \div \dfrac{1}{2}

(318185)÷12=(1554014440)÷12=1140÷12=1140×2=2240=1120.\Rightarrow \left(\dfrac{31}{8} - \dfrac{18}{5}\right) \div \dfrac{1}{2} = \left(\dfrac{155}{40} - \dfrac{144}{40}\right) \div \dfrac{1}{2} \\[1em] = \dfrac{11}{40} \div \dfrac{1}{2} \\[1em] = \dfrac{11}{40} \times 2 \\[1em] = \dfrac{22}{40} \\[1em] = \dfrac{11}{20}.

Hence, (378335)÷12=1120\left(3\dfrac{7}{8} - 3\dfrac{3}{5}\right) \div \dfrac{1}{2} = \dfrac{11}{20}.

Question 4(v)

Simplify:

47÷(13×245)\dfrac{4}{7} \div \left(\dfrac{1}{3} \times 2\dfrac{4}{5}\right)

Answer

Using BODMAS we simplify bracket first.

47÷(13×245)\dfrac{4}{7} \div \left(\dfrac{1}{3} \times 2\dfrac{4}{5}\right)

47÷(13×145)=47÷1415=47×1514=6098=3049.\Rightarrow \dfrac{4}{7} \div \left(\dfrac{1}{3} \times \dfrac{14}{5}\right) = \dfrac{4}{7} \div \dfrac{14}{15} \\[1em] = \dfrac{4}{7} \times \dfrac{15}{14} \\[1em] = \dfrac{60}{98} \\[1em] = \dfrac{30}{49}.

Hence, 47÷(13×245)=3049\dfrac{4}{7} \div \left(\dfrac{1}{3} \times 2\dfrac{4}{5}\right) = \dfrac{30}{49}.

Question 5(i)

Simplify:

(12+13)÷(1416)\left(\dfrac{1}{2} + \dfrac{1}{3}\right) \div \left(\dfrac{1}{4} - \dfrac{1}{6}\right)

Answer

(12+13)÷(1416)\left(\dfrac{1}{2} + \dfrac{1}{3}\right) \div \left(\dfrac{1}{4} - \dfrac{1}{6}\right)

Using BODMAS we simplify bracket first.

(36+26)÷(312212)=56÷112=56×12=10.\Rightarrow \left(\dfrac{3}{6} + \dfrac{2}{6}\right) \div \left(\dfrac{3}{12} - \dfrac{2}{12}\right) = \dfrac{5}{6} \div \dfrac{1}{12} \\[1em] = \dfrac{5}{6} \times 12 \\[1em] = 10.

Hence, (12+13)÷(1416)=10\left(\dfrac{1}{2} + \dfrac{1}{3}\right) \div \left(\dfrac{1}{4} - \dfrac{1}{6}\right) = 10.

Question 5(ii)

Simplify:

(2435÷67+59)×34\left(\dfrac{24}{35} \div \dfrac{6}{7} + \dfrac{5}{9}\right) \times \dfrac{3}{4}

Answer

(2435÷67+59)×34\left(\dfrac{24}{35} \div \dfrac{6}{7} + \dfrac{5}{9}\right) \times \dfrac{3}{4}

Using BODMAS, we solve the division inside the bracket first,

2435÷67=2435×76=45.(45+59)×34=(3645+2545)×34=6145×34=183180=6160=1160.\Rightarrow \dfrac{24}{35} \div \dfrac{6}{7} = \dfrac{24}{35} \times \dfrac{7}{6} = \dfrac{4}{5}.\\[1em] \Rightarrow \left(\dfrac{4}{5} + \dfrac{5}{9}\right) \times \dfrac{3}{4} = \left(\dfrac{36}{45} + \dfrac{25}{45}\right) \times \dfrac{3}{4} \\[1em] = \dfrac{61}{45} \times \dfrac{3}{4} \\[1em] = \dfrac{183}{180} \\[1em] = \dfrac{61}{60} \\[1em] = 1\dfrac{1}{60}.

Hence, (2435÷67+59)×34=1160\left(\dfrac{24}{35} \div \dfrac{6}{7} + \dfrac{5}{9}\right) \times \dfrac{3}{4} = 1\dfrac{1}{60}.

Question 5(iii)

Simplify:

34 of 61823 of 214\dfrac{3}{4} \text{ of } 6\dfrac{1}{8} - \dfrac{2}{3} \text{ of } 2\dfrac{1}{4}

Answer

34 of 61823 of 214\dfrac{3}{4} \text{ of } 6\dfrac{1}{8} - \dfrac{2}{3} \text{ of } 2\dfrac{1}{4}

Using BODMAS, we solve 'of' first,

34 of 618=34×498=14732.23 of 214=23×94=32.1473232=147324832=9932=3332.\Rightarrow \dfrac{3}{4} \text{ of } 6\dfrac{1}{8} = \dfrac{3}{4} \times \dfrac{49}{8} = \dfrac{147}{32}.\\[1em] \Rightarrow \dfrac{2}{3} \text{ of } 2\dfrac{1}{4} = \dfrac{2}{3} \times \dfrac{9}{4} = \dfrac{3}{2}.\\[1em] \Rightarrow \dfrac{147}{32} - \dfrac{3}{2} = \dfrac{147}{32} - \dfrac{48}{32} \\[1em] = \dfrac{99}{32} \\[1em] = 3\dfrac{3}{32}.

Hence, 34 of 61823 of 214=3332\dfrac{3}{4} \text{ of } 6\dfrac{1}{8} - \dfrac{2}{3} \text{ of } 2\dfrac{1}{4} = 3\dfrac{3}{32}.

Question 5(iv)

Simplify:

730 of (13+715)÷(5635)\dfrac{7}{30} \text{ of } \left(\dfrac{1}{3} + \dfrac{7}{15}\right) \div \left(\dfrac{5}{6} - \dfrac{3}{5}\right)

Answer

730 of (13+715)÷(5635)\dfrac{7}{30} \text{ of } \left(\dfrac{1}{3} + \dfrac{7}{15}\right) \div \left(\dfrac{5}{6} - \dfrac{3}{5}\right)

Using BODMAS, we simplify the brackets first,

13+715=515+715=1215=45.5635=25301830=730.730 of 45÷730=730×45÷730=28150÷730=28150×307=45.\Rightarrow \dfrac{1}{3} + \dfrac{7}{15} = \dfrac{5}{15} + \dfrac{7}{15} = \dfrac{12}{15} = \dfrac{4}{5}.\\[1em] \Rightarrow \dfrac{5}{6} - \dfrac{3}{5} = \dfrac{25}{30} - \dfrac{18}{30} = \dfrac{7}{30}.\\[1em] \Rightarrow \dfrac{7}{30} \text{ of } \dfrac{4}{5} \div \dfrac{7}{30} = \dfrac{7}{30} \times \dfrac{4}{5} \div \dfrac{7}{30} \\[1em] = \dfrac{28}{150} \div \dfrac{7}{30} \\[1em] = \dfrac{28}{150} \times \dfrac{30}{7} \\[1em] = \dfrac{4}{5}.

Hence, 730 of (13+715)÷(5635)=45\dfrac{7}{30} \text{ of } \left(\dfrac{1}{3} + \dfrac{7}{15}\right) \div \left(\dfrac{5}{6} - \dfrac{3}{5}\right) = \dfrac{4}{5}.

Question 5(v)

Simplify:

212312×134+2122\dfrac{1}{2} - 3\dfrac{1}{2} \times 1\dfrac{3}{4} + 2\dfrac{1}{2}

Answer

212312×134+2122\dfrac{1}{2} - 3\dfrac{1}{2} \times 1\dfrac{3}{4} + 2\dfrac{1}{2}

Using BODMAS, we solve the multiplication first,

312×134=72×74=498.212498+212=52498+52=208498+208=98=118.\Rightarrow 3\dfrac{1}{2} \times 1\dfrac{3}{4} = \dfrac{7}{2} \times \dfrac{7}{4} = \dfrac{49}{8}.\\[1em] \Rightarrow 2\dfrac{1}{2} - \dfrac{49}{8} + 2\dfrac{1}{2} = \dfrac{5}{2} - \dfrac{49}{8} + \dfrac{5}{2} \\[1em] = \dfrac{20}{8} - \dfrac{49}{8} + \dfrac{20}{8} \\[1em] = \dfrac{-9}{8} \\[1em] = -1\dfrac{1}{8}.

Hence, 212312×134+212=1182\dfrac{1}{2} - 3\dfrac{1}{2} \times 1\dfrac{3}{4} + 2\dfrac{1}{2} = -1\dfrac{1}{8}.

Question 5(vi)

Simplify:

457(318÷1112)4\dfrac{5}{7}\left(3\dfrac{1}{8} \div \dfrac{11}{12}\right)

Answer

457(318÷1112)4\dfrac{5}{7}\left(3\dfrac{1}{8} \div \dfrac{11}{12}\right)

Using BODMAS, we simplify the bracket first,

318÷1112=258×1211=30088=7522.457×7522=337×7522=33×757×22=2475154=22514=16114.\Rightarrow 3\dfrac{1}{8} \div \dfrac{11}{12} = \dfrac{25}{8} \times \dfrac{12}{11} = \dfrac{300}{88} = \dfrac{75}{22}.\\[1em] \Rightarrow 4\dfrac{5}{7} \times \dfrac{75}{22} = \dfrac{33}{7} \times \dfrac{75}{22} \\[1em] = \dfrac{33 \times 75}{7 \times 22} \\[1em] = \dfrac{2475}{154} \\[1em] = \dfrac{225}{14} \\[1em] = 16\dfrac{1}{14}.

Hence, 457(318÷1112)=161144\dfrac{5}{7}\left(3\dfrac{1}{8} \div \dfrac{11}{12}\right) = 16\dfrac{1}{14}.

Question 5(vii)

Simplify:

25 of (17112) of 125\dfrac{2}{5} \text{ of } \left(\dfrac{1}{7} - \dfrac{1}{12}\right) \text{ of } 1\dfrac{2}{5}

Answer

25 of (17112) of 125\dfrac{2}{5} \text{ of } \left(\dfrac{1}{7} - \dfrac{1}{12}\right) \text{ of } 1\dfrac{2}{5}

Using BODMAS, we simplify the bracket first,

17112=1284784=584.25 of 584 of 125=25×584×75=2×5×75×84×5=702100=130.\Rightarrow \dfrac{1}{7} - \dfrac{1}{12} = \dfrac{12}{84} - \dfrac{7}{84} = \dfrac{5}{84}.\\[1em] \Rightarrow \dfrac{2}{5} \text{ of } \dfrac{5}{84} \text{ of } 1\dfrac{2}{5} = \dfrac{2}{5} \times \dfrac{5}{84} \times \dfrac{7}{5} \\[1em] = \dfrac{2 \times 5 \times 7}{5 \times 84 \times 5} \\[1em] = \dfrac{70}{2100} \\[1em] = \dfrac{1}{30}.

Hence, 25 of (17112) of 125=130\dfrac{2}{5} \text{ of } \left(\dfrac{1}{7} - \dfrac{1}{12}\right) \text{ of } 1\dfrac{2}{5} = \dfrac{1}{30}.

Question 5(viii)

Simplify:

(1213)(3445)÷(1225+17)\left(\dfrac{1}{2} - \dfrac{1}{3}\right)\left(\dfrac{3}{4} - \dfrac{4}{5}\right) \div \left(\dfrac{1}{2} - \dfrac{2}{5} + \dfrac{1}{7}\right)

Answer

(1213)(3445)÷(1225+17)\left(\dfrac{1}{2} - \dfrac{1}{3}\right)\left(\dfrac{3}{4} - \dfrac{4}{5}\right) \div \left(\dfrac{1}{2} - \dfrac{2}{5} + \dfrac{1}{7}\right)

Using BODMAS, we simplify the brackets first,

1213=3626=16.3445=15201620=120.1225+17=35702870+1070=1770.16×120÷1770=1120×7017=702040=7204.\Rightarrow \dfrac{1}{2} - \dfrac{1}{3} = \dfrac{3}{6} - \dfrac{2}{6} = \dfrac{1}{6}.\\[1em] \Rightarrow \dfrac{3}{4} - \dfrac{4}{5} = \dfrac{15}{20} - \dfrac{16}{20} = \dfrac{-1}{20}.\\[1em] \Rightarrow \dfrac{1}{2} - \dfrac{2}{5} + \dfrac{1}{7} = \dfrac{35}{70} - \dfrac{28}{70} + \dfrac{10}{70} = \dfrac{17}{70}.\\[1em] \Rightarrow \dfrac{1}{6} \times \dfrac{-1}{20} \div \dfrac{17}{70} = \dfrac{-1}{120} \times \dfrac{70}{17} \\[1em] = \dfrac{-70}{2040} \\[1em] = \dfrac{-7}{204}.

Hence, (1213)(3445)÷(1225+17)=7204\left(\dfrac{1}{2} - \dfrac{1}{3}\right)\left(\dfrac{3}{4} - \dfrac{4}{5}\right) \div \left(\dfrac{1}{2} - \dfrac{2}{5} + \dfrac{1}{7}\right) = \dfrac{-7}{204}.

Question 5(ix)

Simplify:

5635(13+211)\dfrac{5}{6} - \dfrac{3}{5}\left(\dfrac{1}{3} + \dfrac{2}{11}\right)

Answer

5635(13+211)\dfrac{5}{6} - \dfrac{3}{5}\left(\dfrac{1}{3} + \dfrac{2}{11}\right)

Using BODMAS, we simplify the bracket first,

13+211=1133+633=1733.5635×1733=5651165=561755=275330102330=173330.\Rightarrow \dfrac{1}{3} + \dfrac{2}{11} = \dfrac{11}{33} + \dfrac{6}{33} = \dfrac{17}{33}.\\[1em] \Rightarrow \dfrac{5}{6} - \dfrac{3}{5} \times \dfrac{17}{33} = \dfrac{5}{6} - \dfrac{51}{165} \\[1em] = \dfrac{5}{6} - \dfrac{17}{55} \\[1em] = \dfrac{275}{330} - \dfrac{102}{330} \\[1em] = \dfrac{173}{330}.

Hence, 5635(13+211)=173330\dfrac{5}{6} - \dfrac{3}{5}\left(\dfrac{1}{3} + \dfrac{2}{11}\right) = \dfrac{173}{330}.

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