Multiple choice

A and B are two alloys in which ratios of Zinc and Sulphur are 4:5 and 6:7 respectively. If these equally amount of two alloys are melted and made alloy C. What will be the ratio of Zinc and Sulphur in alloy C?

  1. $27:32$
  2. $32:27$
  3. $15:22$
  4. $22:15$

  5. None of these
Reveal answer Fill a bubble to check yourself
E Correct answer
Explanation

Alloy A: Zn:S = 4:5. Total parts = 9. Fraction of Zn = 4/9, S = 5/9. Alloy B: Zn:S = 6:7. Total parts = 13. Fraction of Zn = 6/13, S = 7/13. When equal amounts are mixed, average fraction of Zn = (4/9 + 6/13)/2 = (52/117 + 54/117)/2 = (106/117)/2 = 53/117. Average fraction of S = (5/9 + 7/13)/2 = (65/117 + 63/117)/2 = (128/117)/2 = 64/117. Ratio Zn:S = 53:64. None of the given options match.

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