Question 1050225
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The Cunninghams are moving across the country.  Mr. Cunningham leaves 3.5 hours before Mrs. Cunningham.  
If he averages 50 mph and she averages 70 mph, how long will it take Mrs. Cunningham to overtake Mr. Cunningham? Solve.
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There are 2 (two) ways to solve the problem


<B>Solution 1</U>

<pre>
Your governing equation is 

50*(t+3.5) = 70*t.    (1)

The left side is the distance Mr. Cunningham covered from the start to the overtaking point.

The right side is the distance Ms. Cunningham covered from the start to the overtaking point.

The distances are the same, it gives you the equation (1).

"t" is the time counted from Ms. Cunningham start to the overtaking moment.
(t+3.5) is the time for Mr. Cunningham on his way.

Now simplify and solve the equation (1).

50t + 175 = 70t,  or

175 = 70t - 50t,  or  20t = 175,  or t = {{{175/20}}} = {{{35/4}}} hours = 8 hours and 45 minutes.
</pre>

<B>Solution 2</U>

<pre>
After 3.5 hours driving Mr. Cunningham is 3.5*50 = 175 miles ahead.
Their relative speed is (70-50) = 20 mph.
The time to overtake is {{{175/20}}} = {{{35/4}}} hours = 8 hours and 45 minutes. The same answer.
</pre>

Solved.


See the lesson

&nbsp;&nbsp;&nbsp;&nbsp;- <A HREF=http://www.algebra.com/algebra/homework/word/travel/Travel-and-Distance-problems.lesson>Travel and Distance problems</A>  

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