Question

A and B can do a certain piece of work in 12 days. B and C can the work in 15 days. C and A can do the work in 20 days. How much time will A take to compelete the qork alone?

Answer 1

Answer:

30 days

Step-by-step explanation:

a+b=12

b+c=15

C+a=20

A and B do (1/12)th of the work in a day.

B and C do (1/15)th of the work in a day.

C and A do (1/20)th of the work in a day.

Adding the three, 2A+2B+2C = (1/12)+(1/15)+(1/20) = (25/300)+(20/300)+(15/300) = (60/300) or (1/5)

Hence A + B + C = (1/10)th of the work in a day.

Thus A does (1/10)-(1/15) = (3/30)-(2/30) = (1/30)th of the work in a day.