Question

The ratio of three numbers 4 ∶ 3 ∶ 7. If the sum of their squares is 666. What is the value of the largest of the three numbers?

• A. 21
• B. 28
• C. 14
• D. 17

Answer 1

Answer:

A. 21

Let the numbers be 4x, 3x and 7x
(4x)2  + (3x)2 + (7x)2 = 666
⇒ 16x2 + 9x2 + 49x2 = 666
⇒ 74x2 = 666
⇒ x2 = 9
⇒ x = 3
Largest number = 7x = 7 × 3 = 21