Worked examples
Two examples
Example 1
A bag holds 3 red and 7 blue marbles. What is the probability of NOT red?
- P(red) = 310. The two add to 1.
- 1 − 310.
Answer: 710
Example 2
The chance of rain is 30%. What is the chance it does not rain?
- 100% − 30%.
Answer: 70%
Where this is taught: Quiz 34: Probability and Counting, “The other side: what does not happen”
The drill
Ten problems
How many:
Type a fraction in simplest form, like 2/5, or the number asked for (the % sign is already there). Then press Check my answers at the bottom.Write your answer on the line, or circle it. The answer key, with the reasoning, is on the last page.