WAEC 2011 Mathematics · Question 19

If N112.00 exchanges for D14.95, calculate the value of D1.00 in naira

Options

  1. A.0.13
  2. B.7.49
  3. C.8.00
  4. D.13.00

Answer: B. 7.49

Explanation written with AI and checked against the answer key

Analyze the question: We are told that N112.00 = D14.95 (naira to dalasi). We need the naira value of D1.00.

Concept: To find the value of one unit of a currency, divide the naira amount by the number of units it buys.

Solution:

D14.95 = N112.00

D1.00 = N112.00 ÷ 14.95

Estimate: 14.95 ≈ 15, and 112 ÷ 15 ≈ 7.47.

Exact calculation:

  • 14.95 × 7 = 104.65
  • 112 − 104.65 = 7.35
  • 7.35 ÷ 14.95 ≈ 0.49

So 112 ÷ 14.95 ≈ 7.49

Check: 14.95 × 7.49 = 111.98, which is approximately 112. ✔

Answer: D1.00 ≈ N7.49, which is option B.

Why not the others?

  • A (0.13) is 14.95 ÷ 112, which is the value of N1 in dalasi (the inverse).
  • C (8.00) and D (13.00) do not match the calculation.

Tip: Always check which currency you are converting to. If you want "1 unit of X in terms of Y", divide Y's amount by X's amount. A quick estimate (rounding 14.95 to 15) helps you rule out wrong options fast.

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