Question 1208018: The time t that it takes to get to school varies inversely with your average speed s.
(a) Suppose that it takes you 40 minutes to get to school when your average speed is 30 miles per hour. Express the driving time to school in terms of average speed.
(b) Suppose that your average speed to school is 40 miles per hour. How long will it take you to get to school?
Found 4 solutions by josgarithmetic, timofer, greenestamps, ikleyn:
Answer by josgarithmetic(39617)   (Show Source):
Answer by timofer(104) (Show Source):
Answer by greenestamps(13200)  (Show Source):
You can put this solution on YOUR website!
In the problem, speeds are in miles per hour and times are in minutes.
In general, you can get into all kinds of trouble if you work a problem with mixed units. It would be better mathematics if you change miles per hour to miles per minute, or change minutes to hours.
However, in this simple problem, working with mixed units is okay.
The way the problem is posed, you are apparently supposed to use the result from part (a) to find the answer to part (b).
However, finding the answer to part (b) is trivial if you use the fact that, because of the inverse variation (using mixed units!), the product of the speed in miles per hour and the time in minutes is constant:
30mph * 40 minutes = 40mph * x minutes
30*40 = 40*x
Trivially, the answer is 30 (minutes)
Answer by ikleyn(52786)  (Show Source):
You can put this solution on YOUR website! .
If you will solve such problems in moderate quantifies (let say, 1 - 2 - 3 tasks at a time),
then you can learn a formal approach to solving them.
This, however, will add practically nothing to the overall meaning and to the common sense.
But if you will solve such problems in excessive quantities (5 - 6 at a time),
then instead of acquiring common sense, you will observe the opposite process.
What I want to say is keeping a right balance/measure is important in order for
do not hurt yourself, because these tasks themselves have little content.
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