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Math Help - Word problem

  1. #1
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    Word problem

    1. The distance from school to the
    beach is 10 miles. If you bike from school to the beach in 40 minutes, what is your average speed for the trip? What does this mean?


    I think the average speed is 15miles/hour.
    But what am I suppose to be looking for to answer what does this mean?


    2. On the return trip from the beach, you pedal hard for the first ten minutes and cover 4 miles. Tired, you slow down and cover the last 6 miles in 36 minutes. What is your average speed for the return trip?

    I got 5/23 miles/min. Is this correct?

    Thanks.

    Vicky.
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  2. #2
    Super Member
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    Quote Originally Posted by Vicky1997 View Post
    1. The distance from school to the
    beach is 10 miles. If you bike from school to the beach in 40 minutes, what is your average speed for the trip? What does this mean?
    \begin{aligned}<br />
d &= rt \\<br />
10 &= \frac{2}{3}r\;\;\;\;{\color{red}\text{(because 40 min = 2/3 hr)}} \\<br />
r &= 15\;\text{mph}<br />
\end{aligned}

    You're right that the average speed is 15 mph. As to "what does this mean," well, this is the average speed. You're not going to be traveling at exactly 15 mph for the entire trip. Right when you start and stop the trip, the speed will be close to 0 mph, and sometimes you'll be going over 15 mph.

    2. On the return trip from the beach, you pedal hard for the first ten minutes and cover 4 miles. Tired, you slow down and cover the last 6 miles in 36 minutes. What is your average speed for the return trip?

    I got 5/23 miles/min. Is this correct?
    The total distance is still 10 miles. The total time it took was 46 minutes, or 23/30 hr.

    \begin{aligned}<br />
d &= rt \\<br />
10 &= \frac{23}{30}r \\<br />
r &= \frac{300}{23} \\<br />
&\approx 13.04\;\text{mph} \\<br />
\end{aligned}

    which is 5/23 miles/min. (However, you should use the same units, mph, as in the first part, so you should state the answer as 13.04 mph.)


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  3. #3
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    california
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    Thank you!!!!!
    You made everything so clear now!!!
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