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JAMB Mathematics 1999 Question 35

Question 35

Integration

Find the volume of solid generated when the area enclosed by y = 0, y = 2x and x = 3 is rotated about the x-axis.

  1. A.81π cubic units
  2. B.36π cubic units
  3. C.18π cubic units
  4. D.9π cubic units
Show the answer and explanation

Answer: B (36π cubic units)

Explanation

V = π∫₀³ y² dx = π∫₀³ 4x² dx = π × 4 × 27/3 = 36π cubic units (a cone of radius 6 and height 3).