Ratio and Proportion Cheat Sheet, Summaries of Elementary Mathematics

Download Ratio and Proportion Cheat Sheet and more Summaries Elementary Mathematics in PDF only on Docsity! Ratio and Proportion Cheat Sheet 1. Writing a Ratio: a. The quantity written first is the numerator b. The word “to” separates the quantities c. The quantity written second is the denominator d. Always write in lowest terms, and always as a fraction Example: Write the ratio of 60 days of sun to 20 days of rain. e. Ratios are written with LIKE terms Example: 2 days to 8 hours *2 days = 48 hours 2. Using Mixed Numbers in Ratios: a. Write out the ratio b. Write numbers as improper fractions c. Rewrite the problem horizontally, using the ÷ symbol d. Change the ÷ to × and flip the second term Example: 2 days to 2 1 4 days 3. Writing Rates: *Units are not the same and need to be included as part of the rate* a. Write the rate as a fraction in lowest terms Example: 160 dollars for 8 hours ÷ 2 60 20 = 30 10 = 3 1 ÷ 10 leave as a fraction 48 8 = 6 1 ÷ 8 2 2 1 4 = 2 1 9 4 = 2 1 ÷ 9 4 = 2 1 × 9 4 = 8 9 lowest terms 160 𝑑𝑜𝑙𝑙𝑎𝑟𝑠 8 ℎ𝑜𝑢𝑟𝑠 = 20 𝑑𝑜𝑙𝑙𝑎𝑟𝑠 1 ℎ𝑜𝑢𝑟 4. Finding Unit Rates: *Denominator is 1* a. Write the rate as a fraction b. Divide top number by the bottom number Example: $810 in 6 days 5. Finding the Best Buy: *The best buy is the item with the lowest cost per unit* a. Divide the total price by the number of units b. Round to the thousandths if necessary c. Compare to find the lowest cost per unit Example: Find the best buy for cereal. 12 ounces for $2.49 14 ounces for $2.89 $810 6 𝑑𝑎𝑦𝑠 135 6 810 -6 21 -18 30 -30 0 $135/day use “per” or “/” to write unit rates 0.2075 12 2.49 _ _ -2.4 09 -0 90 -84 60 -60 0 0.20642 14 2.89_ _ _ -2.8 09 -0 90 -84 60 -56 40 -28 12 $0.2064/oz *best buy