Question

Rahul alone can build a room in 20 days.He starts the work and leaves it after 5 days. Arjun does the remaining work in 12 days. how long will it take if arjun did the whole work alone? how long will it take if Rahul and Arjun work together from the beginning?​

Answer 1

Answer:

let the work done by Rahul be x

work done by him in 1 day =

$\frac{x}{20}$

for five days the work completed,

$\frac{5x}{20} \\ \\ = \frac{x}{4}$

Remaining work =

$\frac{3x}{4}$

Arjun completes the remaining work in 12 days

$\frac{3x}{4}$

: 12 ::x : y days

y = 16 days

Arjun alone completes in 16 days

Work done by Rahul in one day =

$\frac{x}{20} </p><p></p><p>$

Work done by Arjun in one day =

$\frac{x}{16}$

$= \frac{x}{20} + \frac{x}{16} </p><p>$

$= \frac{4x + 5x}{80}$

$= \frac{9x}{80}$

$x = \frac{80}{9}$

$x = 9$

if Arjun and Rahul work together from the beginning, they will finish the work in 9 days

hope it helps you ☺️☺️