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3 kg of a solution contains 40% of alcohol by weight. How much alcohol should be added...

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christiano-cr7 | Salutatorian

Posted October 2, 2013 at 6:16 PM via web

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3 kg of a solution contains 40% of alcohol by weight. How much alcohol should be added to obtain a solution containing 50% of alcohol by weight?

A. 0.3 kg

B. 0.6 kg

C. 0.75 kg

D. 1.5 kg

E. 3.75 kg

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2 Answers | Add Yours

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jeew-m | College Teacher | (Level 1) Educator Emeritus

Posted October 2, 2013 at 6:26 PM (Answer #1)

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Let us say we need to add xkg of alcohol to make it 50% by weight.

Amount of alcohol in 40% solution `= 40/100xx3 = 1.2kg`

In the new mixture the weight percentage of alcohol is 50%.

In this solution we have (1.2+x) of alcohol and the total weight of the solution would be 3+x.

`(1.2+x)/(3+x)xx100 = 50`

`2(1.2+x) = 3+x`

`x = 0.6`

So we need to add another 0.6kg of alcohol. Correct answer is at option B.

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wanderista | Student , Grade 11 | Valedictorian

Posted October 8, 2013 at 12:05 AM (Answer #2)

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Option B is the correct option.

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