Mia and Ria can do a piece of work alone in 15 days and 10 days respectively. Mia started the work alone and then after 5 days, Ria joined her till the completion of the work. How long did the work last?
Show answer & explanation
Correct answer: B
Explanation
The correct answer is option 2 i.e. 9 days.
Mia can do a piece of work alone = 15 days
Ria can do a piece of work alone = 10 days
Total work = LCM of 15 and 10 = 30 unit
Efficiency = Total work/Total days
So, efficiency of Mia = 30/15 = 2 unit per day
Ria = 30/10 = 3 units per day
5 days work of Mia = 5 × 2 = 10 unit
Remaining work = 30 - 10 = 20 unit
So, total days to finish the task = 5 days + [20/(2 + 3)] = 5 + 4 = 9 days