Worked examples
Two examples
Example 1
A bag holds 3 red, 5 blue and 2 green marbles. What is the probability of red or green?
- A marble cannot be both, so add: 310 + 210 = 510.
Answer: 12
Example 2
You roll a number cube. What is the probability of an even number or a 5?
- Even: 2, 4, 6. Or 5: four numbers in all.
- 46 = 23.
Answer: 23
Where this is taught: Quiz 34: Probability and Counting, “Zero, one, and the room between”
The drill
Ten problems
This drill also has challenge problems. They use the same skill, set up the way the GED test sometimes sets up a problem, so that it looks new at first.
How many:
Type a fraction with a slash, like 3/4, and a mixed number with a space, like 2 1/4. Give answers in simplest form. Then press Check my answers at the bottom.Write each answer on the line, in simplest form. The answer key, with the reasoning, is on the last page.