Question

If I can paint a wall in 20 min and my friend can paint a wall in 30 min. How many minutes would it take for us to paint a wall working together.

Answer 1

Answer:
`12\ \text{min}`

Explanation:

Given

It takes 20 min and 30 min for a person and his friend to paint a wall individually i.e.

In 1 min they cover
`(1)/(20)` part and
`(1)/(30)` part of wall respectively.

If the work together, 1 minute work is

`\Rightarrow (1)/(20)+(1)/(30)\\\\\Rightarrow (3+2)/(60)\\\\\Rightarrow (5)/(60)`

Time required will be reciprocal of it

`\Rightarrow (60)/(5)=12\ \text{min}`