Alloy A and B contains Tin and Copper in the ratio 5:3 and 2:5 respectively. In waht ratio A and B should be mixed to get a new alloy containing Tin and Copper in the ratio 4:3 ?
Let the Tin and Copper in alloy A is 5x/8 and 3x/8 respectively.
And Tin and Copper in alloy B is 2y/7 and 5y/7 respectively.
Now, required ratio = (5x/8 + 2y/7) / (3x/8 + 5y/7) = 4/3
(35x+16y)*3 = (21x+40y)*4
Solving, we get x/y=16/3
Alternate Method (by alligation rule):
Tin in alloys A and B=5/8 and 2/7
Tin in final alloy = 4/7
5/8 ------------------------- 2/7
--------------- 4/7 ------------
(4/7 - 2/7) ------------ (5/8 - 4/7)
= 2/7 ------------------ 3/56
Ratio = (2/7) / (3/56) = 16/3