And / or probability
The question
P(red or round) from red 4 round, 2 square · blue 3 round, 3 square
4 + 2 + 3 + 3=12
4 + 2 + 3 + 3=12
4 + 2 + 3=9
=
- Count everything first: 4 + 2 + 3 + 3 = 12 counters altogether. That is the bottom of the fraction.
- "Or" means a counter counts if either is true, so it is more than one group: 4 + 2 + 3 = 9. The groups do not overlap.
- 9 out of 12 is in bigger pieces.
How it works.
- 01
Count everything first: 4 + 2 + 3 + 3 = 12 counters altogether. That is the bottom of the fraction.
- 02
"Or" means a counter counts if either is true, so it is more than one group: 4 + 2 + 3 = 9. The groups do not overlap.
- 03
9 out of 12 is 3/4 in bigger pieces.