Mathematics for IGCSE & O level - Proportion (Section 2 - No. 16)
If *y* varies jointly as *x* and the square of *z*, and *y* = 18 when *x* = 2 and *z* = 3, what is *y* when *x* = 4 and *z* = 2?
8
12
16
24
Forklaring
y=kx*z^2, 18=k*2*9, k=1, Therefore, y = 1*4*2^2=16.