If 25 is the sum of ages of X, Y and Z and if X is 17 years younger than Z who is thrice as old as Y. Then how old is Z?

Aptitude and Logical Reasoning Solved Problems:

If 25 is the sum of ages of X, Y and Z and if X is 17 years younger than Z who is thrice as old as Y. Then how old is Z?

Answer : 18

Solution :

Let Y's age be a.

Then Z's age is 3a.

And X's age = 3a-17.

Now, a + 3a + 3a-17 = 25.

7a - 17 = 25.

7a = 25 + 17 = 42

a = 6.

Therefore, Z's age = 3(6) = 18.