Mathematics for IGCSE & O level - Proportion (Section 1 - No. 20)
If *y* varies jointly as *x* and the square root of *z*, and *y* = 12 when *x* = 2 and *z* = 9, find *y* when *x* = 4 and *z* = 4.
8
12
16
24
Giải thích
y= kxsqrt(z), and 12 = k*2*3, thus k=2. Hence y = 2*4*sqrt(4) = 2*4*2=16