The variable cost (V) of manufacturing a product varies according to the equation V = 4q where q is the quantity produced. The fixed cost (F) of production of the same product reduces with q according to the equation F = 400/q. How many units should be produced to minimize the total cost (V + F)? A. 5 B. 4 C. 7 D. 6

GATE 2011 · General Aptitude · Cost Market Price · medium

Answer: Among the given options, q = 5 units yields the minimum total cost of Rs.100.

  1. Differentiate Total Cost: dC/dq = 4 - 400/q^2
  2. Find Theoretical Minimum: q = 10 is the unconstrained minimum (not among the options).
  3. Evaluate C at Each Option: C(4) = 16 + 100 = 116; C(5) = 20 + 80 = 100; C(6) = 24 + 66.7 = 90.7; C(7) = 28 + 57.1 = 85.1