Aptitude - Problems on Numbers - Discussion

Thanks guys.

X+Y = 25... (1)
X-Y = 13...(2)

when we add this we get X = 19... But how see below..
lets take two numbers as X and Y... then..
sum of two number is 25... means X + Y = 25..
and their difference is 13... means X - Y = 13...
but when we add both...

X + Y = 25
+ X - Y = 13
------------------
2X = 38.........

(+Y and -Y gets substracted so above X plus below X is equal to 2X and 25+13 equals to 38)

when we get 2X = 38 then.
X = 38/2 = 19
then if X + Y = 25 then....
19 + Y = 25
Y = 25 - 19 = 6...
we get X = 19 and Y = 6 then.

Find their product... means X * Y = ?
X * Y = 19 * 6 = 114
So Product for this is equal to 114.

Please, can anyone explain this in easy way?

Why we are taking x+y and x-y, and another doubt is why we have to take 4xy?

Please clarify this term.

I am a primary school student, I have a doubt, anyone please clarify this. How to solve this question without taking the unknown variable X & Y?

Thanks @Prashanth.

How to substitute the value of x and y?

Find the value of the variable X and Y separately and find the product of both.

How 4xy?

Ans: Because there two number is 25 & for that's 2+.

(X+Y-X-Y=2xy).

That's why 2+2xy=4xy.

Why taken 4xy?