If q^(-a) = 1/r and r^(-b) = 1/s and s^(-c) = 1/q, the value of abc is:
A. (rqs)^(-1) B. 0 C. 1 D. r + q + s
GATE 2016 · General Aptitude · Fractions · medium
Answer: The value of abc is 1.
- Rewrite all three equations with positive exponents: Eq 1: q^a = r. Eq 2: r^b = s. Eq 3: s^c = q.
- Substitute Eq 1 into Eq 2 to get q^(ab) = s: Since r = q^a, we have s = r^b = (q^a)^b = q^(ab).
- Substitute into Eq 3 to get q^(abc) = q, then read off abc: q^(abc) = q^1 => abc = 1.