Question

Silver and copper are mixed in the ratios 2:5 and 4:7 to prepare two alloys A and B. Equal quantities of these alloys A and B are mixed to prepare a third alloy C. The ratio of silver and copper in C is
(1) 3:5
(2) 25:52
(3) 25:49
(4) 15:27

Answer 1

Solution

Let 1 kg of each one of A and B be taken to form 2 kg of C.
Gold in 1 kg of A = 7/9, copper in 1 kg of A = 2/9
Gold in 1 kg of B = 7/18, copper in 1 kg of B = 11/18
Gold in 2 kg of C = (7/9 + 7/18) = 21/18 = 7/6
Copper in 2 kg of C = (2/9 + 11/18) = 15/18 = 5/6
Ratio of gold and copper in C = 7/6 : 5/6 = 7:5