If x is inversely proportional to y and x 2 fra... - JAMB Mathematics 2010 Question
If x is inversely proportional to y and x = 2\(\frac{1}{2}\) when y = 2, find x if y = 4
A
4
B
5
C
1\(\frac{1}{4}\)
D
2\(\frac{1}{4}\)
correct option: c
x \(\alpha\) \(\frac{1}{y}\) .........(1)
x = k x \(\frac{1}{y}\) .........(2)
When x = 2\(\frac{1}{2}\)
= \(\frac{5}{2}\), y = 2
(2) becomes \(\frac{5}{2}\) = k x \(\frac{1}{2}\)
giving k = 5
from (2), x = \(\frac{5}{y}\)
so when y =4, x = \(\frac{5}{y}\) = 1\(\frac{1}{4}\)
x = k x \(\frac{1}{y}\) .........(2)
When x = 2\(\frac{1}{2}\)
= \(\frac{5}{2}\), y = 2
(2) becomes \(\frac{5}{2}\) = k x \(\frac{1}{2}\)
giving k = 5
from (2), x = \(\frac{5}{y}\)
so when y =4, x = \(\frac{5}{y}\) = 1\(\frac{1}{4}\)
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