An alloy of copper and aluminium has 40% copper. An alloy of copper and zinc and zinc in the ration of 2 : 7. These two alloys are mixed in such way that in the overall alloy, there is more aluminium than zinc and copper constitute XY of this alloy. What is the range of values X can take?
Answer & explanation
Correct answer: option 3
Alloy 1 Copper Aluminium
2x 3x
Alloy 2 Copper Aluminium
2y 7y
If Aluminium and Zinc have to be equal, 3x = 7y. The simplest case occurs at the LCM, when both Aluminium and Zinc are 21kg.
Alloy 1 Copper Aluminium
14 21
Alloy 2 Copper Aluminium
6 21
Even a gram of alloy 1 above this level would mean that there is more Aluminium than Zinc in the total alloy. So, this table is a limit on the percentages of different metals.
The percentage of Copper in the total alloy would be (14 + 6)* 100/62 = 32.25%
32.25% ≤ X ≤ 40%