A can do a certain work in the same time that B and C together can do it. If A and B together could do it in 10 days and C alone in 40 days, then A alone could do it in:
Show answer & explanation
Correct answer: A
Explanation
Given:
A can do the same amount of work as B and C together.
A + B = 10 days
C = 40 days
Let
A = a, B = b, C = c
A can do the same amount of work as B + C. ⇒ a = b + c
A + B = 1/10
⇒ (b + c) + b = 1/10
⇒ 2b + c = 1/10
C = 1/40
2b + 1/40 = 1/10
2b = 1/10 − 1/40
= (4 − 1) / 40
= 3/40
b = 3/80
Now
a = b + c
= 3/80 + 1/40 = 5/80
= 1/16
A's time = 16 days