Ramu works 4 times as fast as Somu. If Somu can complete a work in 20 days independently, then the number of days in which Ramu and Somu together can complete the work is:

4 days

According to the question,

Ramu works 4 times as fast as Somu, therefore,

Ramu : Somu = 4 : 1 (Efficiency)

⇒ Somu completes a work in 20 days,

⇒ Total work = 1 x 20 = 20 units     ..(Efficiency × Days = Total work)

⇒ Time required by Ramu and Somu to complete the work together = \(\frac{20}{4+1}\) = \(\frac{20}{5}\) = 4 days,     ..(\(\frac{Work}{Efficiency}\) = Time)