If y varies directly as the square root of x an... - JAMB Mathematics 2010 Question
If y varies directly as the square root of x and y =3 when x = 16, calculate y when x = 64
A
6
B
12
C
3
D
5
correct option: a
y = \(\alpha\)√x ........(1)
y = k√x ........(2)
When y = 3, x = 16,
(2) becomes 3 = k√16 or 3 = k x 4
giving k = \(\frac{3}{4}\)
from (2), y = \(\frac{3}{4}\)√x
When x = 64, y = \(\frac{3}{4}\)√64
y = \(\frac{3}{4}\) x 8
= 6
y = k√x ........(2)
When y = 3, x = 16,
(2) becomes 3 = k√16 or 3 = k x 4
giving k = \(\frac{3}{4}\)
from (2), y = \(\frac{3}{4}\)√x
When x = 64, y = \(\frac{3}{4}\)√64
y = \(\frac{3}{4}\) x 8
= 6
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