Mathematics for IGCSE & O level - Proportion (Section 1 - No. 35)
If *x* varies inversely as the square of *y*, and *x* = 4 when *y* = 3, what is the formula connecting *x* and *y*?
x = 36/y^2
x = 12/y^2
x = y^2/36
x = 4/y^2
Explication
x = k/y^2; 4 = k/9; k = 36; Thus x=36/y^2.