Gold is 19 times as heavy as water and copper is 9 times as heavy as water. In what ratio should these be mixed to get an alloy 15 times as heavy as water?
Explanation
The most efficient way to solve this is using the Rule of Alligation. Let the weight of water be w. Then the weight of gold is 19w, copper is 9w, and the required alloy is 15w.
1. Apply the Alligation Formula
We compare the densities of the two metals against the mean (target) density:
The ratio of Gold to Copper is calculated as:
Ratio (Gold : Copper)=G−MM−C
2. Calculation
Substitute the values into the formula:
3. Simplify the Ratio
Divide both numbers by their greatest common divisor, which is 2:
So, the metals should be mixed in the ratio of 3 : 2.
Final Answer
To achieve an alloy that is 15 times as heavy as water, gold and copper must be mixed in a ratio of 3 : 2.
The correct option is (c).