Question

a and b can do 1 piece of work in 10 days B and C in 15 days C and A in 18 days.In how many days can B alone do the same work?

30
20
12
18
please explain step by step​

Answer 1

Answer:

20 is the best answer for the question

Answer 2

Step-by-step explanation:

We know A and B can do the whole work in 10 days. B and C can do the whole work in 15 days. A and C can do the whole work in 18 days.

So (A and B)'s 1 day work = 1/10

(B and C)'s 1 day work= 1/15

(A and C)'s 1 day work= 1/18

(A+B+B+C+C+A)'s 1 day work= (1/10)+(1/15)+(1/18) = (9+6+5)/90= 20/90=2/9

(A and B and C)'s 1day work = (A+B+B+C+C+A) / 2

(A and B and C)'s 1 day work= (2/9)/2

= 1/9

No. of days taken by B to complete the work alone = {(A and B and C)'s 1 day work} - {( C and A)'s 1 day work}

= 1/9 - 1/18 = (2/18) - (1/18) = 1/18= 18 days

So the answer is 18 days.