If y varies directly with x, and y = 61 when x = 42, find y when x = 54 (consider integral value).

86 78 82 72

78

y ∝ x y = kx (k is a constant) or y/x = k  x   :  y 42 : 61 :: 54 : ? y = $\frac{61\; \times\;54}{42}$    = 78