# The ratio of blue marbles to white marbles in a bag is 4 to 5. At this rate, how many blue marbles are there if there are 15 white marbles?

Nov 14, 2016

By ratio we have 12 blue marbles for 15 white ones

#### Explanation:

$\left(\text{blue")/("white}\right) \to \frac{4}{5}$

Multiply by 1 but where $1 = \frac{3}{3}$ giving

$\left(\text{blue")/("white}\right) \to \frac{4}{5} \equiv \left[\frac{4}{5} \times 1\right] = \left[\frac{4}{5} \times \frac{3}{3}\right] = \frac{12}{15}$

By ratio we have 12 blue marbles for 15 white ones