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Newsroom Math Crib Sheet
By Prof. Steve Doig
Arizona State University
To convert a fraction into a decimal:
Divide the top number by the bottom number
Examples: 5/8 = 0.625
17/64 = 0.265…
To convert a decimal into a percentage:
Multiply by 100 (or simply move the decimal two places to the RIGHT)
Examples: 0.658 = 65.8%
1.255 = 125.5%
To turn a percentage into a decimal:
Divide by 100 (or simply move the decimal two places to the LEFT)
Examples:
43.7% = 0.437
148.2% = 1.482
To get X% of Y:
Turn X% into a decimal, then
multiply
it by Y
Example: 20% of 90 = 0.20 * 90 = 18
130.5% of 45 = 1.305 * 45 = 58.7…
To compare X and Y using percentages (X is what percent of Y?):
X is (X/Y * 100) percent of Y
Example: 5 and 8:
5/8 = .625 = 62.5%, so 5 is 62.5% of 8
Example: 8 and 5:
8/5 = 1.6 = 160%, so 8 is 160% of 5
To compare X and Y using percentage differences:
X is ((X/Y –1) * 100) MORE/LESS than Y
Use MORE THAN if the answer is positive, and LESS THAN if it’s negative
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This note was uploaded on 05/05/2008 for the course MCO 302 taught by Professor Doig during the Fall '07 term at ASU.
 Fall '07
 Doig

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