Question 437074: if it takes 7 1/2 minutes to walk 3/8 of a mile then how long will it take to walk 2 miles
Answer by oberobic(2304)   (Show Source):
You can put this solution on YOUR website! The standard distance formula is: d=rt, where d=distance, r=rate, and t=time.
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We're told:
3/8 mi = 15/2 min * r miles/min
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Note that 7 and 1/2 minutes = 15/2 minutes
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3/8 = 15/2 * r
Multiply both sides by 8
3 = 8*(15/2) * r
3 = 4*15*r
3 = 60r
Divide both sides by 60
3/60 = r
so
r = 3/60
r = 1/20
That means the person is walking at 1/20 of a mile per minute.
"Per minute" is very important because it would be easy to forget and think in "miles per hour."
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Now that we have r, we can plug it into the next distance equation to determine "how long" it will take to walk 2 miles.
2 = 1/20*t
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Multiply both sides by 20 to remove the denominator.
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40 = t
t = 40
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This suggests it will take 40 minutes to walk 2 miles.
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Always check your answer!
In this case we can use proportions.
Is the proportion: 3/8 : 15/2
the same value as: 2 : 40?
Simplifying, 2 : 40 is the same as 1 : 20, which equals 0.05.
So, let's check (3/8)/(15/2).
Using a calculator we find that (3/8)/(15/2) = 0.05.
The proportions are equal, so we know the answer is correct.
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Review the question to make sure you give a clear answer.
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Answer: It will take 40 minutes to walk 2 miles.
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Done.
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