If

*y*varies directly as the square root of*x*and*y*= 3 when*x*= 16. Calculate*y*when*x*= 64-
**A.**

12 -
**B.**

6 -
**C.**

3 -
**D.**

5

##### Correct Answer: Option B

##### Explanation

*y* ∝ √*x**y* = K√*x*

K = ^{y}/_{√x} = ^{3}/_{√16}

= ^{3}/_{4}*y* = ^{3}/_{4}√*x*

= ^{3}/_{4}√64 when x = 64

= ^{3}/_{4} x ^{8}/_{1}

= 6