Correct Answer - Option 4 : A
Given:
A can complete a work in 20 days.
B can complete a work in 15 days
Concept Used:
Total units of work is equal to the LCM of number of days required to complete the work.
Efficiency = Total units of work/Number of days taken
Calculation:
Total units of work, LCM of 20 and 15
Total units of work,
⇒ 60 units
Efficiency of A,
⇒ 60/20
⇒ 3 units/day
Efficiency of B,
⇒ 60/15
⇒ 4 units/day
B worked for 6 days and left,
Total units of work completed by B in 6 days,
⇒ 6 × 4
⇒ 24 units
Remaining units of work completed by A,
⇒ Remaining units of work = 60 – 24
⇒ Remaining units of work = 36 units
Time taken to complete the work,
⇒ 36/3
⇒ 12 days
∴ A can complete the remaining work in 12 days