If Mona and Sona together can finish a typing work in 18 days and Sona alone can finish it in 24 days, find the number of days in which Mona alone can finish the work.
Show answer & explanation
Correct answer: D
Explanation
The correct answer is option 4 i.e. 72
Let the total work to be done be 72 units.
If Sona does it in 24 days alone, she must be doing 72/24 = 3 units a day
And, if Sona and Mona do the work in 18 days. They must be doing 72/18 = 4 days in a day.
And , Mona does 1 unit a day as Mona does rest 3 units a day.
So, Mona will take 72 days to complete the work with a speed of 1 unit a day.