Two alloys, A and B, contain silver and copper in the ratio 5 : 1 and 7 : 2, respectively. Find the ratio in which they must be mixed such that there is 80% of silver.
There is an alloy (A) of silver and copper. A certain weight of this alloy is mixed with 15 kg of pure Silver and melted. The new alloy (B) contains 90% of silver. If the same weight of alloy (A) is mixed with 10kg of a 90% silver alloy, the new alloy (C) is found to contain 84% silver. Find the percentage of silver in (A).