Question

John can do a piece of work in 9 days. But with the help of his classmate, he can do the same work in 3 days. In how many days can his classmate does the work?​

Answer 1

Answer:

His classmate can complete the work in 4.5 days

Step-by-step Explanation :

Given : John can do a piece of work in 9 days.

He and his classmate together complete the same work in 3

days..

To find : In how many days can his classmate does the work = ?

John can complete the work alone in 9 day's --------- ( given )

So John's one day work = 1/9

Let's assume that his classmate work for x day's

Therefore classmates one day work = 1/x

According to given conditions,

1/9 + 1/x = 1/3

1/x = 1/3 - 1/9

= 9-3/27

= 6/27

= 1/4.5

x = 4.5

So, His classmate can complete the work in 4.5 days

Answer 2

$1 \: hour \: work \: of \: John = \frac{1}{9}$

$1 \: hour \: work \: of \: Classmate = \frac{1}{3}$

$1 \: hour \: of \: both = \frac{1}{9} + \frac{1}{3}$

$= \frac{1 + 3}{9}$

$= \frac{4}{9}$

$So \: Together \: can \: do \: this \: job$

$= \frac{9}{4} \times 100$

$= 25 \times 9$

$= 225 \: minutes$