Aptitude - Time and Work - Discussion

How the 0.53333 come 8/15 ?

a/b + c/d.

= a*d/b*d + c*b/b*d.

= ad+cb/b*d.

Maths rule if denominator not equal if equal directly cross multiplication.

Can you explain how is 7/60 came?

Good explanation but I can't understand how the 1- (7/15) is became 8/15.

For 7/60.

It is necessary to add both 1/15 and 1/20.
But the denominators are different.
So first we equals the denominators by multiplying with.
Two different alternatives.

i.e.
1/15*4/4.

Because whenever we want to gave an alternative for multiplying.
It should applicable to both numerator and denominator.
That's why we use 4/4 for 1/15.

As the same way for 1/20.
We multiplying with 3.
i.e.

1/20*3/3.

Why I'm particularly take 4/4 and 3/3 particularly is.
This is the minimum stage to equal both denominators, understand.
Now it is easy to add.

How did you get 7/15 after simplifying 7/60 ? Didn't understand the simplification of 7/60 to 7/15 Please explain.

Work done=>4*(1/15)+4*(1/20) = 7/15.

Remaining work = 1-7/15.
= 8/15.

Option D.

7/60 is the total work done by A and B in day 1.
Therefore for 4 days we will calculate as below.

7/60 *4 means when its multiplication we will divide.
ie. 4/15 = 60 and we need to keep 7 integer as it was.

Therefore we get 7/15.

I don't know, Hope you'll understand this.

A simple logic when its + or - we will cross multiply

And when its * we will divide.

Thanks.

(1/15+1/20) = 7/60.

Explanation:

15 = 5*3.
20 = 5*4.
Here the common nums are 3,4,5.

3*4*5 = 60.
60/15 = 4.
60/20 = 3.
(3/60+4/60) = 7/60.

Why (1 - 7/15) ?

What is total work as 1.