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 do the whole work alone? How long will it
take, if Rahul and Arjun work together from the beginning?​

Answer 1

Step-by-step explanation:

Work by Rahul in a day=1/20

Work by Rahul in 5 days= 1/20.5= 1/4

Work left= 1-1/4= 3/4

Work by Arjun in a day=1/12of 3/4= 1/16

Thus Arjun takes 16 days

Answer 2

(i) Arjun alone completes in 16 days.

(ii) If Rahul and Arjun work together from the beginning, they finish the work in 9 days.

Step-by-step explanation:

Given:

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 do the whole work alone? How long will it take, if Rahul and Arjun work together from the beginning?

Solution:

(i) Work done by Rahul be x

Work done by him  in one day = $\frac{x}{20}$

For five days, the work completed, $\frac{5x}{20} = \frac{x}{4}$

Remaining work = $\frac{3x}{4}$

Arjun comletes the remaining work in 12 days

$\frac{3x}{4}$ : 12 :: x : y days

y= 16 days.  

Arjun alone completes in 16 days.

(ii)

Work done by Rahul in one day = $\frac{x}{20}$

Work done by Arjun in one day = $\frac{x}{16}$

= $\frac{x}{20}$ + $\frac{x}{16}$

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

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

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

x= 9

If Rahul and Arjun work together from the beginning, they finish the work in 9 days.

To know more:

Roshan alone can build a fence in 20 days. he starts the work and leaves it after 5 days. Ramesh does the remaining work in 12 days. how long will it take if Ramesh did the whole work alone? how long will it take if roshan and ramesh work together from beginning?

https://brainly.in/question/1923766