Correct Answer - Option 1 : 5 days
Given:
Work done by A = 15 days
B is 25% more efficient than A
A and B worked together = 4 days
C alone completed the remaining work = 8 days
Formula used:
Work done = Time × Efficiency
Calculation:
B is 25% more efficient than A
⇒ (15 × 100/125)
⇒ 12 days
B can do the work on 12 days
Now,
LCM of 15 and 12 is 60
A's 1 day work = 4 units
B's 1 day work = 5 units
Work done by A and B work together for 4 days = (4 + 5) × 4 = 36 work
Work left = 60 – 36 = 24 units
C can do the remaining work = 24/8 units = 3 units
Now, A, B and C completed the whole work = 60/(4 + 5 + 3)
⇒ 60/12 days
⇒ 5 days
∴ A, B and C completed the same work together in 5 days