Section 2.7 Mixture Applications and Uniform Motion 163 21. If Charlene invests $2000 in a certificate of deposit and d dollars in a stock, write an expression for the total amount she invested. 22. James has $5000 in one savings account. Let y represent the amount he has in another savings account. Write an expression for the total amount of money in both accounts. 23. How much of a 5% ethanol fuel mixture should be mixed with 2000 gal of 10% ethanol fuel mixture to get a mixture that is 9% ethanol. (See Example 2.) 25. A pharmacist needs to mix a 1% saline (salt) solution with 24 milliliters (mL) of a 16% saline solution to obtain a 9% saline solution. How many milliliters of the 1% solution must she use? Concept 3: Applications Involving Uniform Motion 29. a. If a car travels 60 mph for 5 hr, find the distance traveled. b. If a car travels at x miles per hour for 5 hr, write an expression that represents the distance traveled. c. If a car travels at x 12 mph for 5 hr, write an expression that represents the distance traveled. 5% 10% Final Mixture: Ethanol Ethanol 9% Ethanol 50% 80% Final Mixture: Antifreeze Antifreeze 60% Antifreeze Number of gallons of fuel mixture Number of gallons of pure ethanol Number of ounces of solution Number of ounces of pure antifreeze 30. a. If a plane travels 550 mph for 2.5 hr, find the distance traveled. b. If a plane travels at x miles per hour for 2.5 hr, write an expression that represents the distance traveled. c. If a plane travels at x 100 mph for 2.5 hr, write an expression that represents the distance traveled. 24. How many ounces of a 50% antifreeze solution must be mixed with 10 oz of an 80% antifreeze solution to produce a 60% antifreeze solution? 26. A landscaper needs to mix a 75% pesticide solution with 30 gal of a 25% pesticide solution to obtain a 60% pesticide solution. How many gallons of the 75% solution must he use? 27. To clean a concrete driveway, a contractor needs a solution that is 30% acid. How many ounces of a 50% acid solution must be mixed with 15 oz of a 21% solution to obtain a 30% acid solution? 28. A veterinarian needs a mixture that contains 12% of a certain medication to treat an injured bird. How many milliliters of a 16% solution should be mixed with 6 mL of a 7% solution to obtain a solution that is 12% medication? 31. A woman can walk 2 mph faster down a trail to Cochita Lake than she can on the return trip uphill. It takes her 2 hr to get to the lake and 4 hr to return.What is her speed walking down to the lake? (See Example 3.) Distance Rate Time Downhill to the lake Uphill from the lake 32. A car travels 20 mph slower in a bad rain storm than in sunny weather.The car travels the same distance in 2 hr in sunny weather as it does in 3 hr in rainy weather. Find the speed of the car in sunny weather. Distance Rate Time Rain storm Sunny weather
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