Question

Krishna can build a platform in 8 days and
Imran can do the same job in 12 days. They
work together for 2 days and then Krishna has
to leave. How long will Imran take to complete
the remaining work?​

Answer 1

Answer:

12/7 days or 1 ⁵/₇  days

Step-by-step explanation:

Krishna can build a platform in 8 days

so, work done by Krishna in 1 day = 1/8

Imran can do the same job in 12 days.

so, work done by Imran in 1 day = 1/12

They  work together for 2 days and then Krishna has  to leave

so, work done by Krishna in 2 days = 2/8

                                                           = 1/4

work done by Imran in 2 days = 2/12

                                                  = 1/6

total work done in 2 days by both Krishna and Imran = 1/4 + 1/6

                                                                                        = 5/12

∴ total work done is 1  

total work done in 2 days by both Krishna and Imran is 5/12

work to be done by Imran is 1 - 5/12 =  7/12

number of days to complete 7/12 of the work = reciprocal of the work to

                                                                              be done

                                                                         = 12/7 days or 1 ⁵/₇  days  

Answer 2

Answer:

Krishna can do a. work in 8 days

efficiency is 1/8

Imran can do a work in 12 days

efficiency is 1/12

1 day work done by (k+I) is

1/8 + 1/12 = 5/24

day 1 work done is 5/24

day 2 work done is 5/24 + 5/24 = 10/24

= 5/12

so 5/12 work is done to make it total 1 work we have to make it 12/12

so 12/12 - 5/12

ans. is 7 days