Question

a alone can do a piece of work in 10 days and b alone can do it in 15 days. in how many days will a and b together do the same work

Answer 1

Understand carefully what I am doing here,

If a takes 10days to work, then in 1 day he will complete 1/10th work,

If b takes 15 days to work, then in 1 day he will complete 1/15th work,

Let both people together complete the whole work in x days,

Now (1/10 + 1/15)*x = 1,

Here 1 describes the work,
=> Solving for x,
=> (5/30)*x = 1
=> x = 6

Therefore they will take 6 days if they work together,

Hope you understand, Have a great day !