For a probability from a jar, count the beads that match the event and divide by every bead that could be drawn. Either of two colors includes both, so add their counts. Then count every color for the denominator; Desmos can check the totals. The target count goes over the whole jar, not over only the colors you want.
Hints
- Hint 1
The top of a probability fraction counts the outcomes you want. Either red or white includes both groups. What do you get when you add their bead counts?
- Hint 2
The bottom counts the sample space, meaning every bead that could be drawn. The bead comes from the whole jar, so which color must you include even though it isn't one you want?
Step-by-step
Count the target and the whole jar
Step 1Count the beads that match
Either red or white means a bead of either color works. The colors don't overlap, so add their counts. Type in Desmos; it shows beads that match.
- Step 2
Count every bead that could be drawn
The bead is drawn from the whole jar, including the black beads. Add all three colors: type on the next Desmos line; it shows beads in the jar.
- Step 3
Put the matching count over the total
A probability is the number of matching outcomes over the number of possible outcomes, so
The numerator counts both named colors; the denominator counts every bead in the jar. Choice C.