JAMB - Mathematics (2010 - No. 32)
If x is inversely proportional to y and x = 2\(\frac{1}{2}\) when y = 2, find x if y = 4
4
5
1\(\frac{1}{4}\)
2\(\frac{1}{4}\)
Giải thích
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\(\frac{1}{4}\)