Using Ratios to convert FDP

Remember when?

Well now we can use that knowledge to convert between ratios, percent, and decimals!

Ratio to a Percent Part-to-Whole Ratios can be expressed in the form of a percentage. Example: 15 coins out of the total 25 coins in the collection are quarters. What percent of the coin collection are quarters? Part Whole Percent 100 =

15 coins out of the total 25 coins in the collection are quarters 15 coins out of the total 25 coins in the collection are quarters. What percent of the coin collection are quarters? Step One: Write the example as a ratio in fraction form. Step Two: Remember, a Percent is “out of 100”! Set up an equivalent ratio (or proportion)- something “out of 100”. Step Three: Solve for the percent by multiplying or dividing the numerator and denominator by the same nonzero number! 15 quarters 25 coins 15 quarters 25 coins ? 100 = 60 % x4 15 x 4 = 60 15 quarters 25 coins ? 100 60 100 = = x4

Percent of a Number We can also use the percent to help us find the missing part or the whole. Example 1: If there are 20 coins in the collection, find 25% of the total coins. Example 2: If 80% of the collection is 20 coins, how many coins are in the collection?

25 % of the total collection is 5 coins. Example 1: If there are 20 coins in the collection, find 25% of the total coins. Step One: Identify which parts of the proportion you have. Step Two: Solving for the missing value by multiplying or dividing both the numerator and denominator by the same nonzero number. 25 % of the total collection is 5 coins. Step One: Identify which parts of the proportion you have. Step Two: Solving for the missing value by multiplying or dividing both the numerator and denominator by the same nonzero number. 25 % of the total collection is 5 coins. 25% 25% Part Whole Part Whole Percent 100 Percent 100 = 20 coins 20 coins 5 coins ÷ 5 ? 20 coins 25 100 = ÷ 5

Example 2: If 80% of the collection is 20 coins, how many coins are in the collection? Step One: Identify which parts of the proportion you have. Step Two: Solving for the missing value by multiplying or dividing both the numerator and denominator by the same nonzero number. If 80% of the collection is 20 coins, there is 25 coins in the collection. 80% 20 coins Part Whole Percent 100 = ÷ 4 20 coins ? 80 100 = 25 coins ÷ 4

Ratio to a Decimal When ratios are written in the form of a fraction, we can easily convert from the fraction form to a decimal. Example: The Raiders completed 9 out of the 12 field goal attempts. What part of the field goals were completed?

The fraction bar tells you to divide the numerator by the denominator. The Raiders completed 9 out of the 12 field goal attempts. What part of the field goals were completed? Step One: Write the example as a ratio in fraction form. Step Two: Remember, to convert from a fraction to a decimal you divide the numerator by the denominator. Step Three: Divide and Solve! 9 completed 12 total The fraction bar tells you to divide the numerator by the denominator. 9 completed 12 total 9 completed 12 total Field goals were completed 0.75 of the time. = =

On your own.. Try these! In 1980, the Hawks converted the ball 8 out of 32 times on fourth downs. What percent of the time did they convert the ball? 15 out of 30 cookies are chocolate chip. What percent are not chocolate chip? 48% of the doll collection is 96 dolls. How many dolls are in the total collection? In Ms. Haka’s fourth period, the ratio of girls to boys is 9:16. Express the ratio of girls to total students as a decimal. 5. FUN! What percentage of your first name is vowels? HINT: Vowels over total number of letters in your first name.

EXTEND YOUR LEARNING! We have learned: to solve equivalent ratios by multiplying or dividing the numerator and denominator by the same nonzero number. Caution- In some cases we needed to simplify the ratio (with numerator and denominator) to find the missing value, and complete our equivalent statement. Want to look at some 7th grade ways to solve equivalent ratios or proportions? Check out this video! http://www.khanacademy.org/math/cc-seventh-grade-math/cc-7th-ratio-proportion/cc-7th-constructing-proportions/v/find-an-unknown-in-a-proportion You may need to copy and paste into the browser.