Given: Number of days taken, if Heena and Karan work together = 12 days Heena alone completes the work in 18 days. Calculation: Let the number of days taken by Karan to complete work be x. Work done in 1 days by Heena = (1/18) Work done in 1 day by Karan = (1/x) Work done in 1 day when both work together = (1/12) According to question:
(1/18)+(1/x)=1/12⇒1/x=(3−2)/36=1/36
⇒ x = 36 days ∴ Karan completes the work in 36 days.