Sample Page 85
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Example 2: During a winter storm, 20 cm of snow fell. If this were 16% of the total snowfall for the year, what was the total yearly snowfall?
Solution: To solve any problem we must interpret the problem’s data correctly. In the case of percentage problems we must be sure that it always complies with the premise of the percentage concept, namely: Base × Per cent rate = Percentage A ratio shows the relation of one measure to another by division. The per cent rate is a ratio indicating a relation to 100 units. The equivalence of two ratios may be shown by a proportion. The proportion is in fact an extension of the ratio principle, and thus a percentage problem may be solved by expressing its data in the form of the proportion’s equation:
This problem requires us to find the base ( Step 1. Reasoning: The percent is a fraction that always has a denominator of 100. So, 16% must Step 2. Write the data in the form of a proportion equation.
Step 3. Using the proportion’s "rule of three," multiply the terms 100 and 20 and then divide the product by 16 to find (the yearly snowfall). 100 × 20 = 2,000 Answer. Yearly snowfall is 125 cm. Check. The product of the extremes (2,000) equals the product of the means (2,000), and thus the proportion is a true proportion, and the answer 125 cm is correct. |
) when the percent (16%) and the percentage (20 cm) is given. 
. This is the first ratio. Let the 20 cm snow fall, and the letter 
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