1.2 Estimation Techniques 15 In problems similar to Example 7, the number of regions or areas into which you choose to divide the total area is arbitrary. Generally, the more regions, the better the approximation, as long as the region selected is representative of the other regions in the map, diagram, or photo. When you estimate an answer, the amount that your approximation differs from the actual answer will depend on how you round the numbers. For example, in estimating the product of 196,000 0.02520, × using the rounded values 195,000 0.025 × would yield an estimate much closer to the true answer than using the rounded values 200,000 0.03. × Without a calculator, however, the product of 195,000 0.025 × might be more difficult to determine than 200,000 0.03. × When estimating, you need to determine the accuracy desired in your estimate and round the numbers accordingly. Instructor Resources for Section 1.2 in MyLab Math • Objective-Level Videos 1.2 • PowerPoint Lecture Slides 1.2 • MyLab Exercises and Assignments 1.2 Exercises Warm Up Exercises In Exercises 1–2, fill in the blank with an appropriate word, phrase, or symbol(s). 1. The process of arriving at an approximate answer to a question is called ________. Estimation 2. The symbol ≈ means is approximately ________ to. Equal Practice the Skills In Exercises 3–57, your answers may vary from the answers given in the back of the text, depending on how you round your answers. In Exercises 3–12, estimate the answer. There is no one correct estimate. Your answer, however, should be something near the answer given. 3. 39.7 60.3 18 1.8 + + + 120 4. 86 47.2 289.8 532.4 12.8 + + + + 970 5. 197,500 4.063 ÷ 50,000 6. 1,032,645 49,827 ÷ 20 7. × 1776 0.0098 18 8. 0.63 1523 × 900 9. 23.97 7.05 − 17 10. − 400.15 297.87 100 11. 22% of 9116 1800 12. 11% of 8221 800 Problem Solving In Exercises 13–24, estimate the answer. 13. The cost of renting a campsite for one night if the cost for three nights was $91.35 $30 14. The cost of dinner per person if dinner for 8 people costs $210 and they split the bill evenly $25 15. The amount of money Issac spends on fast food in a year if the average amount he spends per month is $47 $600 16. The cost of 19 gallons of gas if one gallon costs $3.11 $60 17. The cost of 5 items at a grocery store if the items cost $7.99, $4.23, $16.82, $3.51, and $20.12 $53 18. The cost of 5 items purchased at a hardware store if the items cost $1.29, $6.86, $12.43, $25.62, and $8.99 $55 19. The total weight of three people on an elevator if their weights are 95 lb, 127 lb, and 210 lb 400 lb 20. The number of months needed to save $400 if you save $23 each month 16 21. A 20% tip on a meal that costs $49.87 $10 22. A 15% tip on a meal that costs $160.36 $24 23. Maria’s average gas mileage for her car, in miles per gallon, if she drives 396 miles and used 20.1 gallons of gasoline 20 miles per gallon 24. Tran’s average gas mileage for his motorcycle, in miles per gallon, if he drives 207 miles and uses 3.8 gallons of gasoline 50 miles per gallon 25. Lawn Mowing Julian mows lawns to help pay for college. He earns $22 per lawn and is currently mowing 18 lawns per week. Estimate Julian’s weekly earnings. $400 SECTION 1.2 DavideAngelini/ Shutterstock
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