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Mathematics

Evaluate :

(i) 712÷43\dfrac{7}{12} ÷ \dfrac{-4}{3}

(ii) 1225÷56\dfrac{-12}{25} ÷ \dfrac{-5}{6}

(iii) 2732÷916\dfrac{-27}{32} ÷ \dfrac{-9}{16}

(iv) 247÷635-2\dfrac{4}{7} ÷ \dfrac{6}{35}

(v) 26÷11326 ÷ \dfrac{-1}{13}

(vi) 125÷5\dfrac{1}{25} ÷ -5

Rational Numbers

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Answer

(i) 712÷43\dfrac{7}{12} ÷ \dfrac{-4}{3}

We have:

712÷43=712×34[Reciprocal of 43 is 34]=712×3×(1)4×(1)[Making denominator positive]=712×34=7×(3)12×4=7×(1)4×4=716\dfrac{7}{12} \div \dfrac{-4}{3} \\[1em] = \dfrac{7}{12} \times \dfrac{3}{-4} \quad \left[\text{Reciprocal of } \dfrac{-4}{3} \text{ is } \dfrac{3}{-4}\right] \\[1em] =\dfrac{7}{12} \times \dfrac{3 \times (-1)}{-4 \times (-1)} \quad \text{[Making denominator positive]} \\[1em] = \dfrac{7}{12} \times \dfrac{-3}{4} \\[1em] = \dfrac{7 \times (-3)}{12 \times 4} \\[1em] = \dfrac{7 \times (-1)}{4 \times 4} \\[1em] = \dfrac{-7}{16}

Hence, the answer is 716\dfrac{-7}{16}

(ii) 1225÷56\dfrac{-12}{25} ÷ \dfrac{-5}{6}

We have:

1225÷56=1225×65[Reciprocal of 56 is 65]=1225×6×(1)5×(1)[Making denominator positive]=1225×65=(12)×(6)25×5=72125\dfrac{-12}{25} \div \dfrac{-5}{6} \\[1em] = \dfrac{-12}{25} \times \dfrac{6}{-5} \quad \left[\text{Reciprocal of } \dfrac{-5}{6} \text{ is } \dfrac{6}{-5}\right] \\[1em] = \dfrac{-12}{25} \times \dfrac{6 \times (-1)}{-5 \times (-1)} \quad \text{[Making denominator positive]} \\[1em] = \dfrac{-12}{25} \times \dfrac{-6}{5} \\[1em] = \dfrac{(-12) \times (-6)}{25 \times 5} \\[1em] = \dfrac{72}{125}

Hence, the answer is 72125\dfrac{72}{125}

(iii) 2732÷916\dfrac{-27}{32} ÷ \dfrac{-9}{16}

We have:

2732÷916=2732×169[Reciprocal of 916 is 169]=2732×16×(1)9×(1)[Making denominator positive]=2732×169=332×161=32×11=(3)×(1)2×1=32\dfrac{-27}{32} \div \dfrac{-9}{16} \\[1em] = \dfrac{-27}{32} \times \dfrac{16}{-9} \quad \left[\text{Reciprocal of } \dfrac{-9}{16} \text{ is } \dfrac{16}{-9}\right] \\[1em] = \dfrac{-27}{32} \times \dfrac{16 \times (-1)}{-9 \times (-1)} \quad \text{[Making denominator positive]} \\[1em] = \dfrac{-27}{32} \times \dfrac{-16}{9} \\[1em] = \dfrac{-3}{32} \times \dfrac{-16}{1} \\[1em] = \dfrac{-3}{2} \times \dfrac{-1}{1} \\[1em] = \dfrac{(-3) \times (-1)}{2 \times 1} \\[1em] = \dfrac{3}{2}

Hence, the answer is 32\dfrac{3}{2}

(iv) 247÷635-2\dfrac{4}{7} ÷ \dfrac{6}{35}

We have:

=247÷635=187÷635=187×356[Reciprocal of 635 is 356]=37×351=31×51=3×51×1=151=15\phantom{=} -2\dfrac{4}{7} ÷ \dfrac{6}{35} \\[1em] = -\dfrac{18}{7} ÷ \dfrac{6}{35} \\[1em] = \dfrac{-18}{7} \times \dfrac{35}{6} \quad \left[\text{Reciprocal of } \dfrac{6}{35} \text{ is } \dfrac{35}{6}\right] \\[1em] = \dfrac{-3}{7} \times \dfrac{35}{1} \\[1em] = \dfrac{-3}{1} \times \dfrac{5}{1} \\[1em] = \dfrac{-3 \times 5}{1 \times 1} \\[1em] = \dfrac{-15}{1} \\[1em] = -15

Hence, the answer is -15

(v) 26÷11326 ÷ \dfrac{-1}{13}

Express 26 as 261\dfrac{26}{1}

We have:

261÷113=261×131[Reciprocal of 113 is 131]=261×13×(1)1×(1)[Making denominator positive]=261×131=26×(13)1×1=3381=338\dfrac{26}{1} \div \dfrac{-1}{13} \\[1em] = \dfrac{26}{1} \times \dfrac{13}{-1} \quad \left[\text{Reciprocal of } \dfrac{-1}{13} \text{ is } \dfrac{13}{-1}\right] \\[1em] = \dfrac{26}{1} \times \dfrac{13 \times (-1)}{-1 \times (-1)} \quad \text{[Making denominator positive]} \\[1em] = \dfrac{26}{1} \times \dfrac{-13}{1} \\[1em] = \dfrac{26 \times (-13)}{1 \times 1} \\[1em] = \dfrac{-338}{1} \\[1em] = -338

Hence, the answer is -338

(vi) 125÷5\dfrac{1}{25} ÷ -5

Express -5 as 51\dfrac{-5}{1}

125÷51=125×15[Reciprocal of 51 is 15]=125×1×(1)5×(1)[Making denominator positive]=125×15=1×(1)25×(5)=1125\dfrac{1}{25} \div \dfrac{-5}{1} \\[1em] = \dfrac{1}{25} \times \dfrac{1}{-5} \quad \left[\text{Reciprocal of } \dfrac{-5}{1} \text{ is } \dfrac{1}{-5}\right] \\[1em] = \dfrac{1}{25} \times \dfrac{1 \times (-1)}{-5 \times (-1)} \quad \text{[Making denominator positive]} \\[1em] = \dfrac{1}{25} \times \dfrac{-1}{5} \\[1em] = \dfrac{1 \times (-1)}{25 \times (5)} \\[1em] = \dfrac{-1}{125} \\[1em]

Hence, the answer is 1125\dfrac{-1}{125}

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