Rahul alone can complete a work in 10 days and Sonu alone can complete the same work in 15 days. If they work together for 4 days then days, then what part of total is left?

1/3

Rahul = 10 days,

Sonu = 15 days,

⇒ According to the question, they both worked for 4 days,

⇒ (3 + 2) x 4 = 20 units,       ..(Efficiency × Days = Total work)

⇒ Remaining work = 30 - 20 = 10 units,

⇒ Part left of total work = \(\frac{Remaining\; work}{Total \; work}\) = \(\frac{10}{30}\) = \(\frac{1}{3}\).