Percentage

If X's income is 25% more than Y's and Y's income is 20% more than Z's, then by what percentage is X's income more than Z's?

Answer
Method 1

Let Y's income be 100.
So, X's income = 125.
Also given that
if Z's income is 100, then Y's income is 120

Let us follow the unitary method
when Y's income is 120, then Z's income is 100.
when Y's income is 100, then Z's income is (100/120) x 100 = 10000/ 120

Now when Z's income is (10000/120), then X's income is 125
So, when Z's income is 100, then X's income = 125 x (120/ 10000) * 100  = 150
So, X's income is 50% more than Z's.

method 2

1.25Y = X, ---------(1)
Y =1.2 Z -----------(2)
substituting (2) in (1), we have
1.25 x 1.2 Z = X
1.50 Z = X
So, X's income is 50% more than Z's income