The number of seats available for Biology and Computer Science in a school is in the ratio 5:8. They are to be increased by 30% and 25% . Find the new ratio.
Correct answer: B. 13:20
- A. 6:10
- B. 13:20
- C. 3:4
- D. 35:33
Explanation
Take the original numbers as 5k and 8k. After the increases they become 5k(1.30) = 6.5k and 8k(1.25) = 10k, so their ratio is 6.5:10 = 13:20. The likely mistake is choosing 6:10 by increasing the first term by 20% or by rounding 6.5 to 6.
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Ratios compare quantities in the same units, while proportions state that two ratios are equal. Problems cover simplification, division in a given ratio, direct and inverse variation, scale, and missing terms, with attention to the difference between a ratio and a fraction representing part of a whole.
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