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Find the mean proportion between 5 and 45.

Correct answer: B. 15

  • A. 9
  • B. 15
  • C. 25
  • D. 50

Explanation

The mean proportion between 5 and 45 is their geometric mean, √(5 × 45) = √225 = 15. Equivalently, 5:15 = 15:45, so 15 is the middle proportional. The likely trap is option a, 9, which is obtained by dividing 45 by 5 instead of taking the square root of their product.

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About Ratio and Proportion

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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