To mix a particular shade of purple paint, red paint and blue paint are mixed in the ratio 5:3. To make 20 gallons of this shade of purple paint, how many gallons of red and blue paint should be used?

quantity of red paint =  12.5 gallons

quantity of blue paint =  7.5  gallons

Step-by-step explanation:

Ratio of red and blue paint : 5:3

in ratio

a:b = ax:bx

let the

quantity of red paint be 5x

quantity of blue paint be 3x

then quantity of purple paint = quantity of red paint  + quantity of blue paint

                                                  = 8x

given quantity of purple paint is 20 gallons

thus,

8x = 20

x = 20/8 = 2.5

thus,

quantity of red paint = 5x = 5*2.5 = 12.5 gallons

quantity of blue paint = 3x = 3x*2.5 = 7.5  gallons