Question

a and b can do a work in 30 days , b and c in 20 days and c and a 15 days. if all of them work together , the time taken to complete the work will be

Answer 1

Answer:

5 days

Step-by-step explanation:

5 days is answer ......................

I THINK

I SOLVED THiS AND MY ANSWER IS 5 DAYS

Answer 2

Answer:

A and B can do a piece of work in 30 days

B and C can do the same in 20 days

C and A can do that work in 15 days

So,

(A+B)'s 1 day work= 1/30

(B+C)'s 1 day work= 1/20

(C+A)'s 1 day work= 1/15

So,

2(A+B+C)'s 1 day work= 1/30+1/20+1/15

$\frac{1}{30} + \frac{1}{20} + \frac{1}{15} = \\ \frac{2}{60} + \frac{3}{60} + \frac{4}{60} = \\ \frac{2 + 3 + 4}{60} = \\ \frac{9}{60 } = \\ \frac{3}{20}$

Now, 3/20 is 2(A+B+C)'s one day work

So, A+B+C's one day work is (3/20)/2

$\frac{3}{20} \times \frac{1}{2 } = \\ \frac{3}{40}$

so, A,B And C can together do the work in 40/3 days.

Hope this helps you.