Aptitude - Time and Work - Discussion

Let's total total work is 1.

A can do in 15 days.
A can do it in 1 days = 1/15.

Similarly B can do it = 1/20.
They work totally in a day = 1/15+1/20 = 7/60.

A and B do together in 4 days.
So work done in 4 days = 7/60x4 = 7/15.

Then left work is, Total work - 4 days work. i.e, 1-7/15 = 8/7 (Ans).

Why they take like this 1-(7/15)?

a = 15, b = 20, together c = 4 but LCM of in this 3 numbers is 60.

So a is 15(4), b is 20(3) and c is 4(15).

The first of 2 function is (4+3) remaining c(15).

The total of LCM(60).

15-7 = 8.

8/60 answer.

@Sassy.

First, we have to calculate the work done for 1 day. For that we have to divide the number of days by 1.

So, A's 1 day work = 1/15 and B's 1 day work = 1/20.

Work done by A and B for 1 day is (1/15)+(1/20) = 7/60.

Here, L.C.M is taken.

As per question given, For 4 days, multiple with 4 then we can get.

Work done by A and B for 4 days = 4(7/60) = 7/15.

Here too L.C.M is taken.

Total work is 1(Assumption).

So,Work left = Total work - Work done by A and B.

Therefore, work left = 1-(7/15) = 8/15.

This is the answer.

I hope this helps you.

Why 300 will come?

(a*b)/a+b = work out.

(15*20)/15+20 = 4.

300/35 = 4.

7/15.

Remaining Work = (1-7/15).

Answer = 8/15.

I'm not getting it at all can someone explain it why 70/60 in the easiest explanation please.

In all these problems total work taken as "1" so we have to remove the resulting answer i.e., 7/15 from total work"1" so remaining work is (1-7/15) i.e., 8/15.

Why are using 1-7/15?

Hi sir,

How would you calculate the 7/16*4 for to knowing the 4/15=60 ?

Please tell me sir.