Unitary Method — Multiple Choice Questions

If the cost of 14 pens is ₹378, what is the cost of 8 such pens?

1. ₹212

2. ₹214

3. ₹216

4. ₹218

Answer

Cost of 14 pens = ₹ 378

Cost of 1 pen = ₹ $\Big(\dfrac{378}{14}\Big)$ = ₹ 27 [Less pens, Less cost]

Cost of 8 pens = ₹ (27 x 8) = ₹ 216 [More pens, More cost]

Hence, option 3 is the correct option.

A rail journey of 50 km costs ₹160. How much will a journey of 80 km cost?

1. ₹260

2. ₹256

3. ₹280

4. none of these

Answer

Cost of a journey of 50 km = ₹ 160

Cost of a journey of 1 km = ₹ $\Big(\dfrac{160}{50}\Big) = \Big(\dfrac{16}{5}\Big)$ [Less distance, Less cost]

Cost of a journey of 80 km = ₹ $\Big(\dfrac{16}{5} \times 80 \Big)$ = ₹ (16 x 16) = ₹ 256 [More distance, More cost]

Hence, option 2 is the correct option.

A car consumes 6 litres of petrol in covering 81 km. How much distance will it cover in 10 litres?

1. 108 km

2. 124 km

3. 135 km

4. 141 km

Answer

In 6 litres of petrol, distance covered = 81 km

In 1 litre of petrol, distance covered = $\Big(\dfrac{81}{6}\Big) \text{ km }= \Big(\dfrac{27}{2}\Big)$ km [Less petrol, Less distance]

In 10 litres of petrol, distance covered = $\Big(\dfrac{27}{2} \times 10 \Big)$ km = (27 x 5) km = 135 km [More petrol, More distance]

Hence, option 3 is the correct option.

A car covers 450 km in $4\dfrac{1}{2}$ hours. How much time will it take in covering 350 km?

1. 3 hours

2. $3\dfrac{1}{4}$ hours

3. $3\dfrac{1}{2}$ hours

4. 4 hours

Answer

Time taken to cover 450 km = $4\dfrac{1}{2} \text{ hours }= \Big(\dfrac{9}{2}\Big)$ hours

Time taken to cover 1 km = $\Big(\dfrac{9}{2} \times \dfrac{1}{450}\Big) \text{ hours }= \Big(\dfrac{1}{100}\Big)$ hours [Less distance, Less time]

Time taken to cover 350 km

= $\Big(\dfrac{1}{100} \times 350 \Big)$ hours

= $\Big(\dfrac{7}{2}\Big)$ hours

= $3\dfrac{1}{2}$ hours [More distance, More time]

Hence, option 3 is the correct option.

If the cost of 5 bars of soap is ₹85, what will be the cost of 1 dozen such bars?

1. ₹238

2. ₹204

3. ₹198

4. ₹208

Answer

1 dozen = 12 bars

Cost of 5 bars of soap = ₹ 85

Cost of 1 bar of soap = ₹ $\Big(\dfrac{85}{5}\Big)$ = ₹ 17 [Less bars, Less cost]

Cost of 12 bars of soap = ₹ (17 x 12) = ₹ 204 [More bars, More cost]

Hence, option 2 is the correct option.

If the cost of 6 note-books is ₹282, what is the cost of 8 such note-books?

1. ₹376

2. ₹243

3. ₹348

4. ₹364

Answer

Cost of 6 note-books = ₹ 282

Cost of 1 note-book = ₹ $\Big(\dfrac{282}{6}\Big)$ = ₹ 47 [Less note-books, Less cost]

Cost of 8 note-books = ₹ (47 x 8) = ₹ 376 [More note-books, More cost]

Hence, option 1 is the correct option.

If the cost of 16 oranges is ₹124, how many oranges can be bought for ₹155?

1. 18

2. 24

3. 20

4. none of these

Answer

For ₹ 124, oranges bought = 16

For ₹ 1, oranges bought = $\Big(\dfrac{16}{124}\Big) = \Big(\dfrac{4}{31}\Big)$ [Less money, Less oranges]

For ₹ 155, oranges bought = $\Big(\dfrac{4}{31} \times 155 \Big)$ = (4 x 5) = 20 [More money, More oranges]

Hence, option 3 is the correct option.

If the cost of 20 packets of 8 pencils each is ₹400, what is the cost of 25 packets of 12 pencils each?

1. ₹725

2. ₹750

3. ₹735

4. ₹760

Answer

Number of pencils in 20 packets of 8 pencils each = (20 x 8) = 160

Number of pencils in 25 packets of 12 pencils each = (25 x 12) = 300

Now, cost of 160 pencils = ₹ 400

Cost of 1 pencil = ₹ $\Big(\dfrac{400}{160}\Big) = \Big(\dfrac{5}{2}\Big)$ [Less pencils, Less cost]

Cost of 300 pencils = ₹ $\Big(\dfrac{5}{2} \times 300 \Big)$ = ₹ (5 x 150) = ₹ 750 [More pencils, More cost]

Hence, option 2 is the correct option.