Chance as a Percent
Part of the Expressions & Data section of Coddy's Pre-Algebra journey. Lesson 35 of 52.
Chances are often given as percents, like a 40% chance of rain. To turn a probability into a percent, multiply the fraction by 100. If 3 of 20 raffle tickets win, the chance of winning is 3/20, and (3/20) × 100 is 15: a 15% chance.
Why 100? A percent counts hundredths: 15% means 15 out of every 100. Multiplying by 100 says how many of every hundred tries would succeed at the same rate. In the raffle, 3 winners in every 20 tickets is 15 winners in every 100.
On the board, write the percent as its number alone: p = 15 stands for 15%. The ends of the scale carry over: a probability of 0 is 0%, and a certainty, 1, is 100%.
Challenge
A bowl holds 24 sweets, and 6 of them are lemon. You take one without looking. Find the chance p of a lemon sweet as a percent: write the probability times 100, then work it out. Write the percent as a number alone.
Test yourselfThis lesson includes a short quiz. Start the lesson to answer it and track your progress.
Test yourselfThis lesson includes a short quiz. Start the lesson to answer it and track your progress.
All lessons in Expressions & Data
1Variables and Expressions
What a Variable IsWriting ExpressionsExpressions from StoriesTwo OperationsRecap: Expressions2Evaluating Expressions
Substituting a ValueNegative InputsPowers in ExpressionsFormulasRecap: Evaluating5Patterns and Sequences
Continuing a PatternThe Common DifferenceThe nth TermWriting the RuleRecap: Sequences3The Distributive Property
Number PropertiesMental MathDistributing LettersDistributing a MinusRecap: Distributing