Question

One student can paint a wall in 10 minutes. another student can paint the same wall in 15 minutes. working together, how long will it take for them to paint the wall?

Answer 1

6 days

Explanation:

Given that one student can paint a wall in 10 minute and another student in 15 minutes.

Since if number of persons increase, painting time decreases, this is a question of inverse proportion

Hence if they work together they can paint in one day

`(1)/(10) +(1)/(15)` part of the work

i.e. work completed in 1 day when they work together

=
`(1)/(10) +(1)/(15) \\=(9+6)/(90) \\=(1)/(6)`

Hence in 6 days they can together complete the full work

Answer 2

the answer:
One student can paint a wall in 10 minutes
another student can paint the same wall in 15 minutes.
If they paint together the wall, the result time will be

15mn - 10mn = 5 mn

proof:
let / = minute


student 1: / / / / / / / / / /


student2: / / / / / / / / / / / / / / /
x----------------------------------------x
already done
the remain time is / / / / / = five minutes