Breaking the balls into 2 halves
Probability
Level
1
I have 100 balls, each painted with exactly 2 of the following colors: red, blue, green, yellow, orange.
I know that
- 10 of these balls are painted red,
- 20 of these balls are painted blue,
- 30 of these balls are painted green, and
- 40 of these balls are painted yellow.
How many of these balls are painted orange?
60
70
80
90
100
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1 solution
The hint is in the title. So there are 200 halves.
10 of these halves are painted red,
20 of these halves are painted blue,
30 of these halves are painted green, and
40 of these halves are painted yellow.
So there are 2 0 0 − ( 1 0 + 2 0 + 3 0 + 4 0 ) = 1 0 0 halves painted orange.
Since two halves of the same ball cannot be the same color, all of them must have orange paint!