th grade math Representing Probability

Objective To write probabilities as fractions, decimals, and percents. Why? To become more familiar with a variety of situations where probability concepts arise naturally, e.g., where or not a game is fair, the likelihood of rain as part of a weather forecast, the probability that a particular ticket will win the state lottery by understanding these as fractions and/or percents.

California State Standards SDP 3.3 : Represent probabilities as ratios, …; decimals between 0 and 1, and percentages between 0 and 100 and verify that the probabilities computed are reasonable … SDP 3.0: Determine theoretical and experimental probabilities and use these to make predictions about events. MR 3.3: Develop generalizations of the results obtained and the strategies used and apply them in new problem situations.

How to Represent Probabilities 1) Read the problem. 2) Write a ratio. The numerator is the ‘asking’ or the favorable outcome. The denominator is the total, or all possible outcomes. 3) Divide the fraction to get the decimal. Move the decimal 2 spaces to the right to make a percent (add %). Remember Ch 9. 4) Check for reasonableness. Use letters: P,R,O,P,O,R,T,I,O,N. P(vowel) Vowels = 4 P = 4 10 = 2 = 0.40 = 40% 5 This seems reasonable because fewer than ½ of letters are vowels.

How to Represent Probabilities 1) Read the problem. 2) Write a ratio. The numerator is the ‘asking’ or the favorable outcome. The denominator is the total, or all possible outcomes. 3) Divide the fraction to get the decimal. Move the decimal 2 spaces to the right to make a percent (add %). Remember Ch 9. 4) Check for reasonableness More likely P(red) from Box 1 or Box 2? Box 1: 3 red out of 8 Box 2: 2 red out of 10 P(Red from Box 1) = 3/8 P(Red from Box 2) = 2/10 3/8 =.375 = 37.5% 2/10 =.20 = 20% P(red) from Box 1 because of the higher %.

Try It! Write P as fraction, decimal, percent. Box 1: blue = 4, red = 3, yellow = 1 (total = 8) 1)P(yellow) 2)P(blue) 3)More likely P(blue) from Box 1 or Box 2? 1)P(yellow) = 1/8 = = 12/5% 2) P(blue) = 4/8 = ½ = 0.5 = 50% 3) P(blue) from Box 1 or Box 2? Box 1 = 4/8 = 50% Box 2 = 4/10= 40% Box 1 > Box 2; 50% > 40%

Objective Review To write probabilities as fractions, decimals, and percents. Why? You have become more familiar with a variety of situations where probability concepts arise naturally, e.g., where or not a game is fair, the likelihood of rain as part of a weather forecast, the probability that a particular ticket will win the state lottery by understanding these as fractions and/or percents. Probabilities can be written as fractions, decimals, and percents.

Independent Practice Complete problems 4-9 Copy original problem first. Show all work! If time, complete Mixed Review: If still more time, work on Accelerated Math.