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JAMB Mathematics 2005 Question 16

Question 16

Variation

The weight W kg of a metal bar varies jointly as its length L metres and the square of its diameter d metres. If W = 140 when d = 4⅔ and L = 54, find d in terms of W and L.

  1. A.√(42W/5L)
  2. B.√(5L/42W)
  3. C.42W/5L
  4. D.5L/42W
Show the answer and explanation

Answer: A (√(42W/5L))

Explanation

W = kLd2: 140 = k × 54 × 196/9 = 1176k, so k = 5/42. Then d2 = W/(kL) = 42W/(5L).