Worked examples
Two examples
Example 1
A bag holds 3 red, 5 blue and 2 green marbles. You pick one. What is the probability it is blue?
- Favorable over all: 5 blue out of 10.
- 510 simplifies to 12.
Answer: 12
Example 2
A spinner has 20 equal sections, 3 of them blue. What is the probability of blue, as a percent?
- 320 = 0.15 = 15%.
Answer: 15%
Where this is taught: Quiz 34: Probability and Counting, “Favorable over all”
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.