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22 votes
22 votes
Light travels at a speed of $1.9\ \times\ 10^5$ miles per second. How far, in miles, does light travel in $30$ seconds?

User Perimosocordiae
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1 Answer

9 votes
9 votes

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Answer:

5.7×10^6 mi

Explanation:

(1.9×10^5 mi/s) × (3.0×10^1 s) = 5.7×10^6 mi

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Additional comment

When I can see that the product will have a mantissa that has a value greater than 10 or less than 1, I like to adjust the factors so the mantissa of the product comes out in the range 1-10. Here, we could adjust 1.9 to 0.19, or 30 to 3.0. We chose the latter.

Moving the decimal point of 30.0 1 place to the left means we increase the corresponding exponent by 1 (from 0 to 1). 30.0×10^0 = 3.00×10^1