Question

- Amar can finish solving an exercise in 2 hours, Brinda in 3 hours and Chinmoy in 4 hours. In how many hours will all the three complete 100 exercises, considering that no two work on same exercise? (A) 93 hours (B) 90 hours (C) 96 hours (D) 99 hours​

Answer 1

Step-by-step explanation:

Step 1.

Amar can finish solving an exercise in 2 hours.

Then in 1 hour, he can finish solving 1/2 of an exercise.

Step 2.

Brinda can finish solving an exercise in 3 hours.

Then in 1 hour, she can finish solving 1/3 of an exercise.

Step 3.

Chinmoy can finish solving an exercise in 4 hours.

Then in 1 hour, he can finish solving 1/4 of an exercise.

Step 4.

In 1 hour, Amar, Brinda and Chinmoy can solve 1/2, 1/3 and 1/4 of an exercise respectively.

Then in 1 hour, together they can solve

(1/2 + 1/3 + 1/4) exercise

= 13/12 exercise

Step 5.

Solving 13/12 exercise, they take 1 hour

Then to solve 100 exercises, they will take

100/(13/12) hours

= 100 × 12/13 hours

= 92.31 hours

= 93 hours (approximately)

Final answer: (A) 93 hours

In 93 hours, all the three complete 100 exercises.

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