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Percents. TEKS 6.3B Lesson 1 (4 th 6 Weeks). Percents. A special ratio that compares a number to 100 using the symbol % Literally means “ per hundred ”. Examples:. If you have 100 marbles and 35 of them are red, then 35% are red
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Percents TEKS 6.3B Lesson 1 (4th 6 Weeks)
Percents • A special ratio that compares a number to 100 using the symbol % • Literally means “per hundred”
Examples: • If you have 100 marbles and 35 of them are red, then 35% are red • If you use 25 out of 100 postage stamps, then you used 25% of your stamps.
If you used 50 out of 200 postage stamps, you used 25% of your stamps. 25 50 = or 25% 200 100
Representing Percents As Fractions and Decimals • A number followed by a percent symbol (%) has a denominator of 100 and can be easily written as a fraction or a decimal.
Example: 35 • 35% = • Which we read as “thirty-five hundredths • Which written as a decimal is 0.35 • Therefore: 35% = 100 35 = 0.35 100
Of course can be simplified by dividing both the numerator (35) and the denominator (100) by 5 35 100 35 5 7 ÷ = 100 5 20
Decimal to Percent Example • 0.8 is read as “eight tenths and is written as the fraction (ratio) which is equivalent to • compares 80 to 100 and can be written as 80% 8 10 80 100 80 100
Or we can change a decimal to a percent by moving the decimal pointtwo places to the right and adding the % symbol 0.8 = 0.80 = 80%
Dr Pepper (DP) • An easy way to remember which way to move the decimal and how many times, is to remember Dr Pepper. To move from a decimal we move the decimal point two places to the right. D P
To move from a percent to a decimal, we drop the percent & add the decimal. Then we move it two places to the left. D P
Examples: 1 • Change to a percent. 3 0 .3 3 First let’s change the fraction to a decimal. 3 1 .0 0 - 9 1 0 9 - 1
Now we have the decimal lets change it to a percent D P 0 . 3 3 % Drop the decimal and add a % sign.
Let’s change 12.5% into a decimal. D P We are going to drop the percent and move the decimal point two places to the left starting where the decimal point already is. 1 2 . 5 %
Let’s change 0.2 to a percent. D P We are going to move the decimal two places to the right. Drop the decimal and add a percent sign. 0 . 2 0 % We are going to add a 0 by the two to hold the place of the ones place.
Last One • 28% of the class failed last weeks pop quiz. Write how many did not fail the quiz as fraction. 9 We know percents are based out of 100. So we are going to subtract 28 from 100. 1 0 0 1 1 2 8 - 7 2
Now we can change 72% to a fraction. Remember fractions are based off of 100. 72 2 36 2 18 ÷ = ÷ = 100 2 50 2 25 But we can reduce.