Question

Copper in two types of brass: Zinc 5: 2 and copper of other copper: Zinc is 15: 7. Mixing two brass in ratio 5: 2: New copper: zinc =?

Answer 1

1st type of brass Zinc :copper is 5: 2

total amount of brass =  5+ 2 =7

part of zinc in the mixture =5/7

part of copper in the mixture =2/7

2nd type of brass coppe :Zinc is 15: 7.

total amount of 2nd type brass =  15+7 =22

part of copper  in the mixture =15/22

part of Zinc in the mixture =7/22

Now two type of brass is mixed Zinc :Zinc is 5: 2

let the mixture be 5 kg :2kg

amount of copper in the 1st type=5/7*5kg =25/7 kg.............[1]

amount of Zinc in the 1st type=2/7*5kg =10/7 kg.........[2]

amount of copper in the 2nd type=15/22*2kg =15/11kg........[3]

amount of Zinc in the 2nd type=7/22*2kg =7/11 kg.......[4]

adding [1] and [3] to get copper

25/7  +15/11=[275+105]/77  =380/77 kg............................[5]

adding [2] and [4] to get Zinc

10/7 +7/11=[110+49]/77 =159/77 kg...................................[6]

∴  requard ratio from [5] and [6] we get =380/77/: 159/77

New copper: Zinc=380: 159  Ans