Mathematics for IGCSE & O level - Proportion (Section 1 - No. 32)
If *y* is inversely proportional to the square root of *x*, and *y* = 6 when *x* = 4, find *y* when *x* = 9.
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9
Explication
y = k/sqrt(x). Substitute values, 6 = k/2, k=12. Then y = 12/sqrt(9) = 4.