Question

A and B can together finish a work 30 days.
They worked together for 20 days and then 8
left after another 20 days. A finished the
remaining work. In how many days A alone
can finish the work?​

Answer 1

Answer:

A will complete the work in 35 days

Step-by-step explanation:

Answer 2

Step-by-step explanation:

Let a be the number of days A finishes a work

and b be the number of days for B to complete same work.

So A completes 1/a of a work per day

and B completes 1/b of a work per day

according to the question

(1/a + 1/b)×30= 1... where 1 is a work done by both in 30 days

30/a + 30/b=1

30/a= 1- 30/b

30/a= (b-30)/b

a= 30b/(b-30) (1)

Now after working for 20 days

work done = ?

let x be the work done by a and b together

so, 1/x is their total work per day

hence, 1/x ×30= 1 = 30/x=1 (2)

and for twenty days,

1/x × 20= ?= 20/x= ? (3)

Cross multiplying both equation

we have, 30/x ×?= 20/x× 1

30×? = 20

?= 2/3

Therefore, they have completed 2/3 of their total work in 20 days,

Now, remaining work = 1-2/3= (3-2)/3= 1/3

A completed this remaining work but in how many days? without this information we can't calculate the work speed of A