Estimation and Percent of a Number

Method

Finding the Percent of a Number

Percents are commonly used in real-life situations. They represent a relative value of something, not the actual value. The percent of a number should be calculated to find the actual value. Consider the following example. 40 % of 86 This expression can be evaluated in three steps.

1
Rewrite the Percent as a Fraction
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First, recall that a percent is the ratio of a number to 100. This fact allows to write a percent as a fraction. n %=n/100 Apply this formula to 40 %. Then, simplify the fraction as much as possible.

40 %
40/100
40 ÷ 20/100 ÷ 20
2/5

Therefore, 40 % is equivalent to 25. Use this piece of information to rewrite the task. 40 % of 86 ⇕ 2/5 of 86

2
Write a Product Expression
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Recall that the word of is often used to indicate a product in math expressions. This means that 25 of 86 is the same as the product of 25 and 86. 2/5 of 86 ⇕ 2/5 * 86 Multiplying a fraction by a number requires multiplying the numerator of the fraction by the number. The denominator remains the same. 2/5 * 86 = 2* 86/5
3
Evaluate the Expression
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Finally, evaluate the expression. Start by performing multiplication in the numerator. Then, calculate the quotient.

2* 86/5
172/5
34.4

Therefore, 40 % of 86 is 34.4.

Extra

Alternative Method
Another method used to calculate the percent of a number is to rewrite the percent as a decimal number. This is done by dividing the percent by 100 which leads to moving the decimal point two places to the left.

40.0 becomes 0.4 after dividing by 100

As shown, 40 % is equivalent to 0.4. The next step is to multiply the decimal number by 86 in order to calculate 40 % of 86. 0.4* 86=34.4 The calculations show that 40 % of 86 is 34.4. The same result was found although the process used to get it was different.

Exercises
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