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Question 971845: David knew he made a mistake when he calculated that Gilda walks 123 miles to the station. Read through David's calculations:
Using d = rt, the distance is the same, but the rate and time are different.
If Gilda misses the train, it means the time t needs 7 more minutes so d = 3(t + 7).
If she gets to the station 5 minutes early means the time t can be 5 minutes less so d = 4(t - 5).
3(t + 7) = 4(t - 5)
3t + 21 = 4t - 20
t = 41
d = rt, so d = 3(41) = 123
Find David's mistake in his calculations. In two or more complete sentences, explain his mistake. Include the correct calculations and solutions in your answer.
Answer by Boreal(15235)   (Show Source):
You can put this solution on YOUR website! I need a bit more information, but what appears to me important is the lack of units.
If she misses the train, the time t needs 7 more MINUTES.
Later on, t =41, that is minutes.
d=rt, and rate (if she is walking, is 3 miles PER HOUR), which is a walking speed.
Given that alone, she walked just over 2 miles, since 3 miles per hour *40 minutes (2/3) hour, is 2 miles.
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