If x – 3 is directly proportional to the square of y and x = 5 when y =2, find x when y = 6.
- A.
30 - B.
21 - C.
16 - D.
12
Correct Answer: Option B
Explanation
(x – 3) ∝ y^{2}
X-3 = Ky^{2}
K = X-3 / y^{2}
= ^{5-2}/_{22}
= ^{2}/_{4}
= ^{1}/_{2}
∴X-3 = ^{1}/_{2}y^{2}
X-3 = ^{1}/_{2}(6)^{2}
X-3 = ^{1}/_{2} x ^{30}/_{1}
X-3 = 18
X = 21