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.

72

Mona + Sona = 18 days, Sona = 24 days,

⇒ Mona + Sona = 4  (Efficiency)

⇒ Mona + 3 = 4

⇒ Mona = 1,

⇒ Time required by Mona to complete total work alone = \(\frac{72}{1}\) = 72 days,   ..(\(\frac{Work}{Efficiency}\) = Time)