Class VI, VII and VIII students can decorate a school reception in 30 days, 15 days and 10 days respectively. How many class VI students should assist 3 students of class VII and 1 student of class VIII to decorate a school reception in 2 days?

Class VI, VII and VIII students can decorate a school reception in 30 days, 15 days and 10 days respectively. How many class VI students should assist 3 students of class VII and 1 student of class VIII to decorate a school reception in 2 days? Correct Answer 6

Given:

Class VI students decorate a reception = 30 days

Class VI students decorate a reception = 15 days

Class VI students decorate a reception = 10 days

Calculation:

Let the number of class VI students required be x

Work done by class VIII student in 1 day = 1/10

Work done by class VII student in 1 day = 1/15

Work done by class VI student in 1 day = 1/30

Work done by class VIII student in 2 days = 2/10

Work done by class VII student in 2 day = 2/15

Work done by class VI student in 2 day = 2/30

Let x students of class VI assist.

3(2/15) + 1(2/10) + x (2/30) = 1

⇒ 2/5 + 1/5 + x/15 = 1

⇒ x/15 = 1 – 3/5

⇒ x/15 = 2/5

⇒ x = 6