Aptitude - Time and Work - Discussion

Let A completes work in x days.
So no of days taken by B to complete the same work will be 3x days.

A takes 60 days less than B.

So 3x-60 = x.
2x = 60.
x = 30 days (number of days taken by A).
3x = 90 days (number of days taken by B).

Work done by A per day is 1/30.
Work done by B per day is 1/90.

Work done the together in 1 day will be (1/30+1/90) = 4/90.

So work done by them in 10 days will be 40/90.

Work done in 20 days 80/90.

Number of days require to do the remaining 10/90 will be 2.5 days.

Ans = 22.5 days.

Let A takes x days and B takes 60+x days.
Its given that A takes 1 days when B takes 3 days.

So,
1/3 = x/x+60.

Cross multiply and we get x = 30 i.e A.
X+60 = 30 + 60 = 90 i.e B.

Remaining as usual.

Simple:

A's work = x.
B's work = y = 3x.

Hence acc. to ques.: 3x - x = 60 ;.
x=30 A's.
y=90 B's.

Now.... 1/30 + 1/90 = 1/z.

z = 90/4 Answer.

Let,

A takes = x days.
B will take = 3x days.

Difference 3x-x = 60.

So 2x = 60.
x = 30 days.

Thus A can do it in 30 days and B in 90 days.

If difference of time is 60 days, B takes 3/2 x 60 = 90 days.

Please explain this statement.

But there is not given difference in question they given A finish work in 60 day?

If B takes y days , A takes (y-60 ) days. Now , their efficiency are A:B = 3x : x.

So total unit of work is 3x*(y- 60 ) man days = x*y man days.

Calculating this we get y = 90. So if B worked for 90 days, A worked for 30 days.

Hence 1/30 + 1/90 = 22 1/2 days :).

No need to do all that simply guess numbers 30 & 90 which is satisfying this then without using pen we can get answer 22.5 days.

Suppose A takes x days.

Then, B will take 3x days.

From question, 3x-x = 60.

=> x = 30.

=> A takes 30 days and B takes 90 days.

Together they will take = 30*90/30+90.

= 30*90/120.

= 90/4.

= 22.5 or 22 1/2 days (ans).

Is there a fixed formula for this?