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8th Grade Math

8th Grade Math Question of the Day

Practice 8th Grade Math with the production-style question-of-the-day selection for this public URL.

Question 1

The mass of a grain of sand is about 0.0000025 kilograms. Which is this value written in scientific notation?

  1. 2.5×10−52.5 \times 10^{-5}2.5×10−5
  2. 2.5×10−62.5 \times 10^{-6}2.5×10−6
  3. 2.5×1062.5 \times 10^{6}2.5×106
  4. 0.25×10−50.25 \times 10^{-5}0.25×10−5
Explanation: Move the decimal six places to the right to get 2.52.52.5, so 0.0000025=2.5×10−60.0000025 = 2.5 \times 10^{-6}0.0000025=2.5×10−6. The negative exponent indicates a small number. Choice A is off by one place. Choice C has the wrong sign. Choice D is equivalent in value but not proper scientific notation because 0.250.250.25 is less than 1.