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 ?
Gold is 19 times as heavy as water i.e G = $$19W$$
Copper is 9 times as heavy as water i.e C = $$9W$$
Let both the metals be mixed in the ratio of $$A : B$$. Then,
$$\frac{A(G)}{A + B} + \frac{B(C)}{A + B} = 15W$$
$$A(19W)+ B(9W) = 15W(A + B)$$
$$19A+ 9B = 15A + 15B$$
$$4A = 6B$$
$$A : B = 3 : 2$$
Hence, option D is the correct answer.
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