Mean is the arithmetic average. 

 Add the numbers, then divide by the number of numbers.

To find the mean of 100, 45, 45, 80, 92:  Add 100+45+45+80+92 = 362 Then 362 ÷ 5 = 72.4

To find the median of 100, 45, 45, 80, 92: Put the numbers in order.  45, 45, 80, 92, 100.  The median is the number in the middle after they are in order.  80  is the median here. 

If there is an even number of numbers, the median is the average of the 2 middle numbers after they are put in order. Example:

65, 80, 70, 50.  Put in order:

60, 65, 70, 80.  65 and 70 are in the middle.  Average them:   65 + 70 = 135.  

                           135 ÷ 2 = 67.5 

67.5  is the median of this set of numbers. 

The mode is the number or numbers which occurs most often.  In the original set of numbers already given.  45 is used most often.

In statistics, range is the difference between the highest number and the smallest number.  In the original set of numbers :  100 – 45 is 55.  The range is 55.

 If these were grades, if there were one more test, could I bring my grade up to a B an 80 average?  Think one more test would be 6 tests, to have an 80 average, that would be like 80 x 6 or 480 points.  The sum is now 362.  Even if I make 100 on the next test, I will only have 462 not the 480 points I need. 

If I take 2 more tests, could I bring my grade up to a B?  2 more tests would be 7 tests TOTAL.  7 x 80 = 560.   362 plus possible 200 = 562, SO it would be possible, but probably not likely.

What if scores are rounded up to the next integer?

You have a 56, 65, and 70.  What would you need on the next test to have a C (69.5 or more).  4 (69.5) = 278.  You now have 56, 65, 70 which adds to 191.  How many more points need to make 278?   278 - 191 = 87.

You would need to make 87 or more on the 4th test.

The following frequency distribution shows the gas mileage for some new cars.  Find the median gas mileage to the nearest tenth.

Using actual numbers  we have:

24, 24, 24, 24, 24, 24, 24, 25, 25, 26, 26, 27

Actual number in the middle when in order is 24, not halfway between 25 and 26 as it might have appeared at first glance.