Why does my child write 0.00045 as 4.5 × 10⁴?
Your child gives a number less than 1 a positive power of 10, such as 0.00045 = 4.5 × 10⁴.
Why children do it
Children count the places the decimal point moves, but not which way. A number less than 1 needs a negative power of 10: 0.00045 is 4.5 divided by 10 four times, which is 4.5 × 10⁻⁴.
How to help at home
Ask them whether the number is bigger or smaller than 1: a small number has a negative power of 10.
The right way
Write in scientific notation: 0.0039
- 0.0039 = 3.9 ÷ 10003.9 is between 1 and 10.
- 3.9 × 10⁻³Dividing by 1000 is 10⁻³: the point moved 3 places.
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