Lisa is an avid runner and is training for a marathon, so she runs everyday to achieve this purpose. In this way, she goes out to run for six days, so we have the following data set regarding the miles she runs:
1st day = 3.2 miles
2nd day = 7.5 miles
3rd day = 9.8 miles
4th day = 11.5 miles
5th day = 2.9 miles
6th day = 3.5 miles
<span>Finally, she ran a total of:
3.2+7.5+9.8+11.5+2.9+3.5 =
38.4 miles
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What was the average distance of each run?
This result can be get as the sum of each run (or the </span>total of miles she run<span>) divided by the numbers of days she ran.
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Lisa's goal for this week is to run an average of 6 miles per day. How many miles does she need to run tomorrow (the 7th day) in order to achieve her goal of 6 miles per day for the week?
Let's name x the distance she must run tomorrow. Therefore, the equation for this purpose is given as follows:
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∴

Isolating x:

∴

Therefore, she need to run:

in order to achieve the goal of 6 miles per day.