If y varies directly as x and inversely as z, and y = 9 when x = 6 and z = 4, what is the value of y when x = 8 and z = 3?
Answer and explanation
Correct answer: B. 16
- Step 1: Joint variation formula: y = k x / z. Step 2. Find k: 9 = k 6 / 4 => 36 = 6k => k = 6. Step 3. When x = 8 and z = 3: y = 6 8 / 3 = 48 / 3 = 16. Answer: 16. Why not the others: k=4.5 leads to y=12, but fails the initial condition 9 = 4.56/4 = 6.75.
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