Single correct option
Alloy A has copper and zinc in the ratio 3:2, while alloy B has copper and zinc in the ratio 1:3. In what ratio should A and B be mixed so that the resulting alloy has equal amounts of copper and zinc?
- A. 2:5
- B. 5:2
- C. 3:4
- D. 4:3
Show answer and solution
Answer: (B) 5:2
In alloy A, copper fraction = 3/5. In alloy B, copper fraction = 1/4. For the mixture to have copper = zinc, the copper fraction of the mixture must be exactly 1/2. By alligation: (3/5 − 1/2) : (1/2 − 1/4) = (1/10) : (1/4) = 2:5, and this ratio applies to A:B in the OPPOSITE order to how alligation values are matched, giving A:B = 5:2. Check: with 5 parts A and 2 parts B, copper = 5(3/5)+2(1/4) = 3+0.5 = 3.5 and zinc = 5(2/5)+2(3/4) = 2+1.5 = 3.5 — equal, confirming 5:2.
Saved on this device. Sign in or create a free account to keep it on every device.