Five years from now, the ratio of the ages of A, B and C will be 3 : 5 : 2. The sum of the squares of their present ages is 525. What is the present age of B?

20 years

Lets assume age of A after Five years = 3x

   ⇒                Age of B after Five years = 5x

   ⇒               Age of C after Five years is = 2x

ATQ,

   ⇒  (3x-5)² + (5x-5)² + (2x-5)² = 525

   ⇒ 9x² + 25 - 30x + 25x² + 25 - 50x + 4x² + 25 - 20x = 525

   ⇒ 38x² - 100x - 450 = 0

   ⇒ 19x² - 50x - 225 = 0

   ⇒ x = 5 or -45/19

As age cannot be negative so x = 5

Age of B after 5 Years = 5 × 5 = 25

age of B = 25 - 5 = 20 years