Question 51: Find the approximate result of the expression (in whole numbers)

 Question 51:

Find the approximate result of the expression (in whole numbers):

49.6×10.2−7.1×29.7−5.1×20.149.6 \times 10.2 - 7.1 \times 29.7 - 5.1 \times 20.1

Options: (a) 390 (b) 290 (c) 209 (d) 190

Step 1: Round the numbers for approximation

  • 49.6≈5049.6 \approx 50, 10.2≈1010.2 \approx 10 → 50×10=50050 \times 10 = 500

  • 7.1≈77.1 \approx 7, 29.7≈3029.7 \approx 30 → 7×30=2107 \times 30 = 210

  • 5.1≈55.1 \approx 5, 20.1≈2020.1 \approx 20 → 5×20=1005 \times 20 = 100

Step 2: Perform the calculation

500−210−100=190500 - 210 - 100 = 190

✅ Answer: (d) 190

Tip for fast calculation:

  • Round off numbers to the nearest whole number before multiplying.

  • Do step-by-step subtraction after approximation.

  • This gives a quick and reasonably accurate result for multiple-choice questions.

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