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13. 12
14. 1, 181, 000, 000, 000
15. 35 × 10 −9
16. 0.0061 × 10 7
17. 100 × 1000
Express the products in scientific notation.
13
8
18. (5 × 10 )(4 × 10 )
15
19. (1.1 × 10 −9 )(9.5 × 10 )
23
20. (6.03 × 10 )(1 × 10 −9 )
4.11 Percents, Conversions
A percent is a fraction in which the denominator is exactly 100. So it is a special type of decimal
fraction. The word “percent” comes from the Latin phrase per centum meaning “out of 100,” and is
symbolized by %. For example,
97
97% means or 0.97.
100
Percents need not be whole numbers, and they need not represent proper fractions. For example,
150
150% = =1.5
100
0.5
0.5% = =0.005
100
Fractions, decimals, and percents represent the same quantities in different ways, and we need to
know how to convert one to another.
A decimal can be converted to a percent by moving the decimal point two places to the right and
adjoining the % symbol. This is the same as multiplying the decimal fraction by 100, which exactly
cancels the denominator, leaving just the numerator (the percent). Thus
0.68 = 68%
2.05 = 205%
0.708 = 70.8%
1.4 = 140%
0.0067 = 0.67%
To convert a percent back into a decimal, we simply divide by 100,which, as we know,is equivalent
to moving the decimal point two places to the left. Thus
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