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

Answer:

6 days

Step-by-step 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

$\frac{1}{10} +\frac{1}{15}$ part of the work

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

=$\frac{1}{10} +\frac{1}{15} \\=\frac{9+6}{90} \\=\frac{1}{6}$

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