CPM Homework Help : MC1 Problem 5-77

The probability of getting a white marble from a bag is $\frac { 1 } { 5 }$ . If there are four white marbles in the bag, what is the total number of marbles in the bag?

Step 1:

$\text{Set up equivalent fractions. } \frac{1}{5} = \frac{4}{?}$

Step 2:

$\text{Solve for the missing denominator. }\frac{1}{5} = \frac{4}{20} \text{ since 20 is four times 5.}$

Answer:

$20$ marbles