Question

Mary alone can finish a painting job in
12 days. Gary alone can do the same job in
20 days. Mary works alone for 4 days and
then Gary joins in to help. In how many days
will they finish the job?
​

Answer 1

Answer:

5 days

Step-by-step explanation:

Work already done by Mary: 4*1/12=1/3

Work Remaining: 1-1/3=2/3

So,

1/12t + 1/20t =2/3

60(1/12t + 1/20t =2/3)

5t + 3t =40

8t=40

t= 5

Hence they will finish the job in 5 days

Answer 2

Given data:

Mary can finish a painting job in = 12 days

Gary alone can do the same job in = 20 days

Mary work alone for = 4 days

Step-by-step explanation:

solution

To find= how many days will they finish the job

solution=

Work done by Mary in 4 days=4*1/12= 1/ 3

Work remaining= 1-1/3=2/3

Combined productivity of both=1/12 +1/20

LCM= 60

= 8/ 60 = 2/15

They take 2/3/(2/15) = 2/3*15/2

= 5 days

So they take 5 days to finish the job after Mary works alone for 4 days.

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