Question

A and B can do a piece of work in 20 days and 30 days respectively. B started the work and after 5 days A joined . find the total time taken to complete the work .


step by step explanations please

right answer according to the answer sheet is 15 days.​

Answer 1

Step-by-step explanation:

1. Let's Assume x be the no. of days taken by A

and x+5 be the no. of days taken by B

2. We have,

A takes 20 days and B takes 30 days to complete the work individually

A=20 , B=30

A/B = 20/30

x/x+5 = 20/30

then cross multiply

x * 30 = 20 ( x+5 )

30x = 20x + 100

30x - 20x = 100

10x = 100

x = 100/10

x = 10

so, A takes 10 days to complete the work together with B

but B started 5 days before than A

B = x + 5

B = 10 + 5

B = 15 days

Therefore, The total time taken to complete the work is 15 days.

I hope it helps.