be emptied in 2 hr. By itself, it takes the small drain 3 hr longer to empty the tank than it takes the large drain to empty the tank on its own. How much time would it take for each drain to empty the pool on its own? 78) Working together, a professor and her teaching assistant can grade a set of exams in 1.2 hr. On her own, the professor can grade the tests 1 hr faster than the teaching assistant can grade them on her own. How long would it take for each person to grade the test by herself ? 79) Miguel took his son to college in Boulder, Colorado, 600 mi from their hometown. On his way home, he was slowed by a snowstorm so that his speed was 10 mph less than when he was driving to Boulder. His total driving time was 22 hr. How fast did Miguel drive on each leg of the trip? 80) Nariko was training for a race and went out for a run. Her speed was 2 mph faster during the fi rst 6 mi than it was for the last 3 mi. If her total running time was 1 3 4 hr, what was her speed on each part of the run? Write an equation and solve. 73) It takes Kevin 3 hr longer than Walter to build a tree house. Together they can do the job in 2 hr. How long would it take each man to build the tree house on his own? 74) It takes one pipe 4 hours more to empty a pool than it takes another pipe to fi ll a pool. If both pipes are accidentally left open, it takes 24 hr to fi ll the pool. How long does it take the single pipe to fi ll the pool? 75) A boat can travel 9 mi downstream and then 6 mi back upstream in 1 hr. If the speed of the current is 3 mph, what is the speed of the boat in still water? 76) A plane can travel 800 mi with the wind and then 650 mi back against the wind in 5 hr. If the wind blows at 30 mph, what is the speed of the plane? 77) A large fi sh tank at an aquarium needs to be emptied so that it can be cleaned. When its large and small drains are opened together, the tank can R1) What does it mean for an equation to be in quadratic form? R2) What is the hardest part of using substitution? R3) Can you solve any of the problems in this section by using two different methods? 644 CHAPTER 10 Quadratic Equations and Functions www.mhhe.com/messersmith
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