The quantity y varies directly as x and inversely as z When x is 10 and z is 4 , y is 15 What is y when x is 20 and z is 6 ?

Since y varies directly as x and inversely as z, y = kx/z for some constant k. Using y = 15, x = 10, and z = 4 gives k = 6; then y = 6 × 20 ÷ 6 = 20, so the answer is 20.

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