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JAMB 2000 · UME · Q5

Evaluate (2.813×10−3)×1.0635.637×10−2\dfrac{(2.813 \times 10^{-3}) \times 1.063}{5.637 \times 10^{-2}}, reducing each number to two significant figures and leaving your answer in two significant figures.

Worked solution (try it first)
  1. Round each number to 2 significant figures: 2.8×10−32.8 \times 10^{-3}, 1.11.1 and 5.6×10−25.6 \times 10^{-2}.
  2. Top: 2.8×1.1=3.082.8 \times 1.1 = 3.08, so the top is 3.08×10−33.08 \times 10^{-3}.
  3. Divide: 3.08÷5.6=0.553.08 \div 5.6 = 0.55, and 10−3÷10−2=10−110^{-3} \div 10^{-2} = 10^{-1}.
  4. So the value is 0.55×10−1=0.0550.55 \times 10^{-1} = 0.055, option B.

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