Sunday, August 29, 2010

Math Tips

Math Tips, Equations

How to Round a Number

To the nearest ten
If the ones digit is 5 or more, round to the next highest ten 
(68 rounds to 70).
If the ones digit is less than 5, round to the next lowest ten
(33 rounds to 30).

To the nearest hundred
If the tens digit is 5 or more, round to the next highest 
hundred (384 rounds to 400).
If the tens digit is less than 5, round to the next lowest 
hundred (427 rounds to 400).

To the nearest thousand
If the hundreds digit is 5 or more, round to the next highest 
thousand (7,602 rounds to 8,000).
If the hundreds digit is less than 5, round to the next lowest 
thousand (7,268 rounds to 7,000).

How to Find an Average

To find the average of several numbers, add the numbers 
together and then divide the 
sum by the number of numbers.
The average of 17, 30, 6, and 7 = 60 ÷ 4 = 15

How to Tell if Two Fractions are Equivalent

Cross multiply the fractions. If both products are the same, 
the fractions are equivalent.
3 and   9       3 x 24 = 72    3 and   9  are equivalent fractions.
8        24       8 x 9   = 72   8        24

5  and   3       5 x12 = 60    5   and  3  are not equivalent fractions. 
8         12       8 x 3 = 24    8        12

Math Tips, Student







How to Find a Percentage
To tell what percentage one number is of a second number, 
divide the first number 
by the second. Move the decimal point of the resulting quotient 
two places to the right.
Example:  What percentage is 20 of 300?
20 ÷ 300 = .067  =  6.7%

How to Change a Fraction to a Percentage

Divide the numerator by the denominator. Move the decimal 
point of the resulting quotient two places to the right.
 6     =   6 ÷ 15 = .4 = .40 = 40%
15

How to Change a Decimal to a Percentage

Move the decimal point two places to the right.
0.792 = 79.2%

1 comment:

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