Question

Raman and Bishnu can do a piece of work in 20 days and 15 days respectively. Raman started the work alone and then after 4 days Bishnu joined him till the completion of the
work. How long did the work last?
O 48/7
O 76/7
040/7
0 43/7​

Answer 1

Answer:

option C is correct.....

Answer 2

Given:

Days required by Raman to complete a work = 20 Days

Days required by Bishnu to complete a work = 20 Days

To find:

Days for which work lasted.

Solution:

One day work of Raman = 1/20

One day work of Bishnu = 1/15

Initially, Raman worked for 4 days alone,

Work done by Raman in 4 days alone = 4/ 20 = 1/5

Remaining work = 1 - (1/5)

Remaining work = 4/5

Now, 4/5 part of the job was done by both Raman and Bishnu.

One day work of Raman and Bishnu = $\frac{1}{20}$+ $\frac{1}{15}$

part of job completed in one day by Raman and Bishnu = 7 / 60

Days required to complete one job = 60/7 days

Days required to complete 4/5 part of the job = (4/5) × ( 60/7)

Days required to complete 4/5 part of the job = 48/7

Hence, the total days for which work lasted is 48/7 days