Mathematics for IGCSE & O level - Proportion (Section 2 - No. 45)
If *y* varies inversely as *x*, and *y* = 2 when *x* = 10, find *y* when *x* = 4.
0.8
5
20
40
คำอธิบาย
If y varies inversely as x, then xy = k. 2*10 = 20, so k = 20. If x=4, then 4y = 20, which makes y=5.