I can solve this problem by trial and error, but what is a clean formula for quickly getting an answer?
Alice leaves her house, driving east at 45 miles per hour (mph). Thirty minutes later, her husband Dave notices she forgot her cell phone and sets off after her. How fast must Dave travel in order to catch up with Alice 3 hours after he leaves?
Alice leaves her house, driving east at 45 miles per hour (mph). Thirty minutes later, her husband Dave notices she forgot her cell phone and sets off after her. How fast must Dave travel in order to catch up with Alice 3 hours after he leaves?
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If x is Dave's speed, then he drives for 3 hours and travels 3x.
Alice travels for 3.5 hours at 45 mph and travels 3.5 x 45 = 157.5 miles.
3x = 157.5
x = 52.5 mph.
Alice travels for 3.5 hours at 45 mph and travels 3.5 x 45 = 157.5 miles.
3x = 157.5
x = 52.5 mph.
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x mph
3x = 3.5(45) ---> x = ...
3x = 3.5(45) ---> x = ...