Multiple choice

The ratio of alcohol to water in a mixture of 170 ml is 7 : 10. When some amount of alcohol was added, the ratio of alcohol to water increased by 25%. The amount of alcohol added is

  1. 18.4 ml

  2. 15.5 ml

  3. 20.4 ml

  4. 17.5 ml

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

Initial mixture: 170 ml, ratio 7:10. Alcohol = 70 ml, Water = 100 ml. New ratio of alcohol to water increases by 25% of the original ratio (7/10 * 1.25 = 8.75/10). New alcohol amount = 8.75/10 * 100 = 87.5 ml. Added alcohol = 87.5 - 70 = 17.5 ml.

AI explanation

The initial amount of alcohol in the 170 ml mixture is (7 / 17) * 170 = 70 ml, and water is 100 ml. A 25% increase on the initial ratio of 7/10 brings the new ratio to 7/8. Letting x be the added alcohol, the equation becomes (70 + x) / 100 = 7 / 8; solving for x gives 17.5 ml of added alcohol.

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