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July 9th, 2017, 08:17 PM  #1 
Newbie Joined: Jun 2017 From: North Texas Posts: 19 Thanks: 1  Help with a KA problem (Slope,speed, rate) 
July 9th, 2017, 09:09 PM  #2 
Senior Member Joined: May 2016 From: USA Posts: 881 Thanks: 353 
Because she did not start right away. She rode at a constant speed once she finished getting ready, but that means that her average speed was not constant from the time she got the call. It was only constant once she started pedaling. She could travel 5 km in 40 minutes after the call, giving an average rate of 0.125 km / min from the time of the call. She could travel 7 km in 52 minutes after the call, giving an average rate of about 0.135 km /min from the time of the call. So let's set it up as a system of equations. $\text {c = time spent cycling}.$ $\text {g = time spent getting ready}.$ $\text {t = total time}.$ $\text {r = constant speed while cycling}.$ $\text {d = distance traveled}.$ $\therefore d = 0 * g + c * r = cr$ because no distance is traveled during g. $\text {And } t = c + g \implies g = (t  c) \implies d = cr = (t  g)r = tr  gr.$ $7 = 52r  gr.$ $5 = 40r  gr.$ $\therefore 7  5 = (52r  gr)  (40r  gr) \implies 2 = 12r.$ What does that mean? It means she pedals 2 kilometers in 12 minutes. So how long does it take her to pedal 1 kilometer? 
July 10th, 2017, 12:17 AM  #3 
Newbie Joined: Jun 2017 From: North Texas Posts: 19 Thanks: 1 
Triple dots = therefore and arrows means implies? right? I quoted your post to see but still getting the symbols down. 
July 10th, 2017, 01:03 AM  #4 
Senior Member Joined: Feb 2016 From: Australia Posts: 1,475 Thanks: 494 Math Focus: Yet to find out.  

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problem, rate, slope, speed 
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