Question

Difficulty: MediumBasic Probability and Counting Methods

A box contains red, blue, and yellow game tokens. The probability of randomly selecting a red token is 38\frac{3}{8}, and the probability of randomly selecting a blue token is 13\frac{1}{3}. If the box contains exactly 1414 yellow tokens, how many total tokens are in the box?

  1. 4848Answer
  2. B
    2424
  3. C
    2222
  4. D
    1616
  5. E
    7272

Answer

There are 48 total tokens in the box.
The total probability of all outcomes in the box must equal 11. Combining the given probabilities for red and blue tokens yields 38+13=924+824=1724\frac{3}{8} + \frac{1}{3} = \frac{9}{24} + \frac{8}{24} = \frac{17}{24}. The remaining probability representing the yellow tokens is 11724=7241 - \frac{17}{24} = \frac{7}{24}. Since the box contains 1414 yellow tokens, setting 724\frac{7}{24} of the total number of tokens equal to 1414 gives 724N=14\frac{7}{24} N = 14, which simplifies to N=48N = 48.

Step-by-Step Solution

1
Find the probability of selecting a red or blue token.
38+13=924+824=1724\frac{3}{8} + \frac{1}{3} = \frac{9}{24} + \frac{8}{24} = \frac{17}{24}
Since selecting a red token and a blue token are mutually exclusive events, add their probabilities using a common denominator of 2424.
2
Calculate the probability of selecting a yellow token.
11724=7241 - \frac{17}{24} = \frac{7}{24}
The sum of the probabilities of all possible outcomes (red, blue, yellow) must equal 11.
3
Set up and solve the equation for the total number of tokens NN.
724N=14    N=14×247=2×24=48\frac{7}{24} N = 14 \implies N = 14 \times \frac{24}{7} = 2 \times 24 = 48
Multiply the count of yellow tokens (1414) by the reciprocal of the yellow token probability (247\frac{24}{7}).

Key Concept

Determining total sample size using complementary probabilities of mutually exclusive events
Estimated Time:1m 15s
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