Leaving from her house Mary leaves Pittsburgh in her car tra

Leaving from her house, Mary leaves Pittsburgh in her car traveling towards Cleveland at 3PM. She travels at an average rate of 30 mi an hour. Mary\'s brother Jack leaves the house an hour later and follows the same route as Mary. He travels at an average rate of 60 mi. hr. How long will it take to catch up to Mary?

Solution

Mary DATA:
rate = 30 mph ; time = x hrs. ; distance = 30x miles
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Jack DATA:
rate = 60 mph ; time = x-1 hrs ; distance = 60(x-1) miles
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Equation:
distance = distance
30x = 60x - 60
30x = 60
x = 2 hrs
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Mary will drive for x = 2 hrs
Jack will crive for x-1 = 1 hr