### Instruction: Jeff's five assignment scores are 89, 92, 88, 95 and 91. What is the arithmetic mean of these five scores?### Response: To find the arithmetic mean of a set of numbers, I need to add up all the numbers and divide by how many there are.
In this case, I have five numbers, so I will add them up and divide by five.
I can use a calculator or do it by hand.
I will do it by hand because it is not too hard.
I can use the commutative property of addition to rearrange the order of the numbers to make it easier.
I will put the numbers in pairs that add up to 180 or 190, like this: 89 + 91, 92 + 88, and 95.
Then I can add up the pairs: 89 + 91 = 180, 92 + 88 = 180, and 95 = 95.
Now I have three numbers that add up to 455: 180 + 180 + 95 = 455.
Finally, I divide by five to get the mean: 455 / 5 = 91.
So the arithmetic mean of Jeff's five assignment scores is 91.