Question

Owen Mixes purple paint. He uses 3 pints of blue paint for every 5 pints of red paint. He has 17 1/2 pints of red paint. How much blue paint does he need? (proportion)

Answer 1

Since the ratio is 3:5 blue:red and we have the red amount we can divide by the red side of the ratio and then multiply by the blue side.
17.5 / 5 = 3.5
3.5 * 3 = 10.5

Or alternatively you can change the ratio to a decimal. 3 / 5 = .6
Now multiply times the red amount. 17.5 * .6 = 10.5<span />