In previous sections, you applied percents in order to solve problems involving discounts, percent increases, and percent decreases. In this section, you will think about different ways that you can estimate when solving problems involving percents. Estimation is an important way to check your answers for reasonableness.

For each problem below, decide which equation you could use to estimate the answer. Drag the tile with the equation next to the correct problem.

Pause and Reflect

How did you use rounding to estimate the solutions to these problems?

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Check Your Answer

Some values were rounded to the nearest 10 or the nearest ten thousand in order to generate numbers that were easier to work with.

How did you determine to which place value to round?

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Check Your Answer

You can obtain a more precise answer by rounding to the smaller place value, but you also want to obtain numbers that are relatively easy to work with. For example, if you round 15,970 to the nearest ten thousand, you have 20,000, but that gives an estimate that is too large. If you round 15,970 to the nearest thousand, you have 16,000, which gives an estimate that is closer to the actual answer.

Practice

1. A carpentry crew for a construction project has 36 workers. One day, many workers stayed home due to illness. Only 29 workers were present that day. About what percent of the work crew was present that day?

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   Need a hint?

   To calculate a percent, determine the ratio of present workers to total workers. Round so that you have compatible numbers.
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   Check Your Answer

   Round 29 to 30, and leave 36 alone.
   
   Present workers over total workers Present Workers Total Workers ≈ 30 over 36 30 36 = 5 over 6 5 6 ≈ 83.3%
   
   About 83% of the work crew was present.
2. A new vehicle has a sale price of $14,599. Marva wants to make a 30% down payment toward the new vehicle. About how much will her down payment be?

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   Need a hint?

   Round the sale price of the vehicle to the nearest thousand.
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   Check Your Answer

   Round 14,599 to 15,000.
   
   15,000 × 30% = 15,000 × 0.30 = 4,500
   
   Marva’s down payment will be about $4,500.
3. A county has 416,387 registered voters. In a recent election, the voter turnout was 19.7%. About how many people voted in the election?

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   Need a hint?

   Round both the number of registered voters and the turnout percentage.
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   Check Your Answer

   Round 416,387 to 400,000, and round 19.7% to 20%.
   
   400,000 × 20% = 400,000 × 0.20 = 80,000
   
   About 80,000 people voted in the recent election.