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Average Speed

 
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novatronics



Joined: 11 Jan 2011
Posts: 1
Location: northern ohio

PostPosted: Wed Jan 12, 2011 2:40 am    Post subject: Average Speed Reply with quote

If a jogger jogs 12meters per second for 15 minutes, what must his final speed be to have an average speed of 9 km/hr if he jogged for another 45 minutes? I need help setting up the equation!
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hepcj
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Joined: 23 Jun 2007
Posts: 125

PostPosted: Thu Feb 03, 2011 7:55 pm    Post subject: Reply with quote

This is about writing an equation and solving to find the unknown speed.
We know the average speed was 9 km/hr over a time of 1 hour and we know the speed for 15 minutes of the run was 12 km/hr

Therefore,

0.25 hr * 12 km/hr + 0.75 hr * x km/hr = 1 hr * 9 km/hr

Solve for x.
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