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JAMB 1990 · UME · Q6

Simplify and express in standard form 0.00275×0.006400.025×0.08\dfrac{0.00275 \times 0.00640}{0.025 \times 0.08}.

Worked solution (try it first)
  1. Top in standard form: 2.75×10−3×6.4×10−3=17.6×10−62.75 \times 10^{-3} \times 6.4 \times 10^{-3} = 17.6 \times 10^{-6}.
  2. Bottom: 2.5×10−2×8×10−2=20×10−42.5 \times 10^{-2} \times 8 \times 10^{-2} = 20 \times 10^{-4}.
  3. Divide: 17.6÷20=0.8817.6 \div 20 = 0.88, and 10−6÷10−4=10−210^{-6} \div 10^{-4} = 10^{-2}, so the value is 0.88×10−20.88 \times 10^{-2}.
  4. In standard form this is 8.8×10−38.8 \times 10^{-3}, option C.

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