Multiple choice

In two types of brass, the ratio of copper and zinc are 8:3 and 15:7 respectively. The ratio in which these two types of brass should be mixed so that the ratio of copper and zinc in this new type of brass becomes 5:2 is-

  1. $5 : 2$
  2. $3 : 2$
  3. $7 : 4$
  4. $2 : 3$
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Let x and y be parts of brass1 and brass2. Set up: (8x/11 + 15y/22) / (3x/11 + 7y/22) = 5/2. Cross-multiply to get 2(16x + 15y) = 5(6x + 7y), which simplifies to 2x = 5y, giving x:y = 5:2.