Civil Services Examination · Question 30
Suppose x, y and z are variables taking positive real numbers as their possible values. It is given that y is directly proportional to x² and x is inversely proportional to z. For z = 7/25, the values of x and y are 5 and 50, respectively. If y = 98, what is z equal to?
Show answer & explanation
Answer: (B) 1/5
Explanation
y ∝ x² and x ∝ 1/z give y ∝ 1/z², so yz² is constant: 50 × (7/25)² = 98 × z², giving z² = 1/25 and z = 1/5.