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
Verified Correct Answer: B.
Step-by-Step Mathematical Solution
(x – 3) ∝ y2
X-3 = Ky2
K = X-3 / y2
= 5-2/22
= 2/4
= 1/2
∴X-3 = 1/2y2
X-3 = 1/2 (6)2
X-3 = 1/2 x 36/1
X-3 = 18
X = 21
Source: Myschool Past Questions Archive (Record #9271)