A and B can complete a certain work in 24 days and 42 days respectively. A started the work and after x days, B joined him and the whole work was completed in 20 days. The value of x is:
Answer & explanation
Correct answer: option 2
A = 24 days, B = 42 days,
⇒ A worked for x days alone = 7x
⇒ Then B joined him and whole work was completed in 20 days, therefore,
⇒ \(\frac{168 - 7x}{11}\) = 20 - x
⇒ 168 - 7x = 220 - 11x
⇒ 11x - 7x = 220 - 168
⇒ 4x = 52
⇒ x = 13.