Hi Atul, the concentration of Alcohol in solution A will be 0.9)^2 = 81%, B will be (0.9)^3 = 72.9% and C will be (0.9)^4 = 65.61%, average of these three is 73.17% which is Option (B).

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mixture ansd alligation image.png 62.9 KB

mixture ansd alligation image.png 62.9 KB