2011 CEMC Gauss (Grade 8) Problems/Problem 5

Problem

A bag contains $15$ balls. Exactly $3$ of these balls are red. Alex reaches into the bag and randomly selects one of the balls. What is the probability that the ball Alex selects is red?

$\text{ (A) }\ \frac{1}{5} \qquad\text{ (B) }\ \frac{4}{5} \qquad\text{ (C) }\ \frac{1}{15} \qquad\text{ (D) }\ \frac{1}{4} \qquad\text{ (E) }\ \frac{14}{15}$

Solution

To find the probability that the ball is red, we can divide the number of balls that are red in the bag, and divide it by the total number of balls. This gives:

$\frac{3}{15} = \frac{3 \div 3}{15 \div 3} = \boxed {\textbf {(A) } \frac{1}{5}}$

~anabel.disher

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2011 CEMC Gauss (Grade 8) Problems/Problem 5

Problem

Solution