Subject: General Aptitude · Chapter: Ratio and Proportion · Exam: 2010 · Marks: · Difficulty:
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?
(a)1 : 1
(b)1 : 2
(c)2 : 3
(d)3 : 2
Answer
Answer (as printed): D
Explanation
$G=19 W$ and $C=9 W$. Let 1 gm of gold be mixed with $x$ gm of copper to get $(1+x) \mathrm{gm}$ of the alloy. $(1 \mathrm{gm}$ gold $)+(x \mathrm{gm}$ copper $)=(x+1)$ gm of alloy $\Leftrightarrow 19 W+9 W x=(x+1) \times 15 W$ $\Leftrightarrow 19+9 x=15(x+1)$ $\Leftrightarrow 6 x=4 \Leftrightarrow x=\frac{2}{3}$. ∴ Ratio of gold and copper $=1: \frac{2}{3}=3: 2$.
Explanation as extracted from the printed page; notation may be imperfect.