Averages & Means
💡The average is the total divided by the count. When numbers are close together, pick a base value and average only the differences from it.
Try it — find the average
liveAdd the values, then divide by how many there are.
- 1
Add them all up
47 + 52 + 48 + 53 = 200
- 2
Divide by the count
200 ÷ 4 = 50
⏱️ Practice against the clock
A worked example
For 47, 52, 48, 53: guess a base of 50. The gaps are −3, +2, −2, +3, which cancel to 0, so the average is exactly 50.
Average the differences, not the numbers
Adding up a column of big, similar numbers is slow and a great way to slip up. There is a nicer route. Pick a round number near the group and only track how far each value drifts from it.
For 47, 52, 48, 53, guess 50. The drifts are −3, +2, −2, +3. They cancel out to zero, so the average is exactly 50. You added four tiny numbers instead of four big ones, and you are done.
Why that is exact, not a guess
The mean of the group is just your base plus the average of those little drifts. Nothing got thrown away, you only moved the arithmetic onto smaller numbers, so the answer is spot on rather than rounded.
Pick a base somewhere in the middle of the pack and the drifts stay small, which keeps the whole thing light enough to do in your head.
Questions people ask
How do I average numbers that are close together fast? ▾
Choose a round base near the group, add up how far each number sits above or below it, and divide that small total by the count. It beats adding large numbers.
What is the difference between mean and average here? ▾
In everyday use they are the same thing: the total shared equally across all the values. These drills use the plain arithmetic mean.