Mathematics for IGCSE & O level - Proportion (Section 2 - No. 32)
If *y* is inversely proportional to *x*2, and *y* = 8 when *x* = 2, what is the value of *y* when *x* = 4?
1
2
4
16
คำอธิบาย
Using the formula y=k/x^2, when y=8 and x=2, we get 8=k/4. So k=32. When x=4, then y=32/16=2.