Lorenzo’s test scores are 90, 83, 88, 74, 68, and 80. if the teacher drops the lowest test score before calculating the mean, what would the new mean be? round to the nearest tenth, if necessary.

To find the mean, add all the values and then divide the sum by how many values you added. In this case, if the teacher drops the lowest score (68) that would leave 5 values. So,

90 + 83 + 88 + 74 + 80 = 415 < this is the total of all (minus the lowest) or Lorenzo's test scores. Now take this number, and divide it by 5 (because we added five tests together):

415 / 5 = 83 < this is the new mean, and also his percentage grade. 

 83

Alternatively, you can list the grades from least to greatest, and cancel one value from each side until you get to the middle.