Question 633948
Mary travels from the city to visit her sister in the country. On the way, she travels 55km/hr. She stays with her sister for 20 hours before starting home. On the return trip, she travels 45 km/hr. She returned home a grand total of 41 hours after she left. How far away, in kilometers, is Mary's house from her sister's? 
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City to Country DATA:
rate = 55 kmh ; time = x hrs ; distance = 55x km
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Country to Cith DATA:
rate = 45 kmh ; time = (21-x) hrs ; distance = 45(21-x) km
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Equation:
distance = distance
55x = 45(21-x)
55x = 45*21 - 45x
100x = 45*21
x = 9.45 hrs (time going city to country)
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Distance = 55x = 55*9.45 = 519.75 km
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Cheers,
Stan H.