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?

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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?

A21

B28

C14

D17

Answer:

A. 21

Read Explanation:

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

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