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Each day, Monday through Friday, Stacy drives the $20$ miles to work and $20$ miles back. On a given week, the city begins construction that affects her driving and causes her to go slower as the week progresses. On Monday, she is able to drive at 60 mph on the way to work, but only 50 mph on the way home. On Tuesday, she can drive 50 mph to work, but only 40 mph home. This drop-by 10 mph continues each day. What is the average of Stacy's five daily average speeds?

 Jul 16, 2020
 #1
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If you make a list of the driving speed, 60,50,50,40,40,30,30,20,20,10 you notice a patern, To avoid any heavy adding and multpling knowing it 

                                                            +10,20,20,30,30,                                                           equals 5 70's is helpful.  To find the average 

                                                              70,70,70,70,70                                                            you need to add all 10 numbers up and then divide it by 10.  We already know tha t divided by 5 it equals 70 so 70 divided by 2 is 35.  So 35 is our answer

 Jul 16, 2020
 #2
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1 - Her average speed on Monday is =40 / (11/15) =54.54 mph
2 - Her average speed on Tuesday is =40 / (9/10) =44.44 mph
3 - Her average speed on Wednesday is =40/ (7/6) =34.29 mph
4 - Her average speed on Thursday is = 40 / (5/3) =24 mph
5 - Her average speed on Friday is =40 / 3 = 13 1/3 mph
6 - Her average speed over the 5-day period =[5 * 40] / [11/15 + 9/10 + 7/6 + 5/3 + 3] =200 / (112/15) =26.786 mph

 Jul 16, 2020

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