What is the average of these test scores: 70, 75, 80, 85, 90?

Average (mean) = sum of values ÷ number of values. Sum: 70 + 75 + 80 + 85 + 90 = 400. Count: 5 values. Average: 400 ÷ 5 = 80. Three types of averages: Mean — what most people call 'average', the sum divided by count. Median — the middle value when sorted (or mean of two middle values if even count); in this case 80 is also the median. Mode — most frequent value. For evenly spaced values, the mean equals the median. The ASVAB often tests problems where you need to find a missing value. Example: 'Three test scores average 80; two of them are 75 and 85. What is the third?' Set up: (75 + 85 + x)/3 = 80; solve: 160 + x = 240; x = 80. To find an average when given one set of data and adding more, use the weighted approach: combined sum ÷ combined count.