A can complete a task in 12 days, B in 18 days. They work together for 3 days. What fraction of work remains?
Show answer & explanation
Correct answer: C
Explanation
The correct answer is option 3 i.e. 7/12.
Total work = LCM of 12 and 18 = 36 units
Efficiency of A = 36 ÷ 12 = 3 units/day
Efficiency of B = 36 ÷ 18 = 2 units/day
Together efficiency = 3 + 2 = 5 units/day
Work done in 3 days = 5 × 3 = 15 units
Remaining work = Total work - Work done = 36 - 15 = 21 units
Fraction of work remaining = 21/36 = 7/12