Question

Paint is red : blue in a ratio of 2 : 4. if 5 litres of red is used how much blue is used

Answer 1

10 litres because in the ratio 2:4

                                                 ↑ Four is double the 2

So this tells us that there is twice as much red paint as there is blue paint. And if there is five litres of red paint then double that is 10, so there is ten litres of blue paint.

Answer 2

10 liters of blue

Hope this helped