2024 · Q6
p varies directly as (x² + y² + z²). When x = 1, y = 2, z = 3, then p = 70. What is the value of p when x = -1, y = 1, z = 5?
Elementary MathematicsRatio and Proportion
- A100
- B125
- C135
- D140
Explanation
p = k(x²+y²+z²). With x=1, y=2, z=3: x²+y²+z² = 14, so 70 = 14k and k = 5. For x=−1, y=1, z=5: x²+y²+z² = 1+1+25 = 27, so p = 5×27 = 135. This is option C.