Aptitude - Time and Work - Discussion

I understood upto 7/15. I can't understand how they are telling total work 1. From that they were minusing 7/15 can you explain me.

@Jansi.

Both A and B doing the same (one) work, not different work.

We have to divide the denominator by its common divisible number and cross multiply it in numerator so you will get 7 then mutilply the highest remainder of lcm with the lowest denominator. You will get answer.

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.