Missing number from the mean worksheets

Finding the mean shares a total out; this runs it backward. These free printable worksheets give a set with one number missing and the mean the whole set should have, and ask what the missing number is — the question that shows whether "the mean is the total shared out" is really understood.

Kid stuck on one? You don’t just get the sheet.

Missing number from the mean
Missing number from the mean worksheet — One value missing, whole answers, free printable with answer key

The answer key prints on a separate page.

What's on this sheet

The step a child skips is the first one: a mean of 8 over five numbers means the five must add to 8 × 5 = 40. Once the total is in hand, the missing number is just what is left after the ones you were given — 40 minus their sum. Every step-by-step walk multiplies the mean up before it subtracts, because that multiplication is the whole idea.

Why this sheet works

It is the exact inverse of the mean sheets, and doing both is what turns the mean from a recipe into a thing a child can reason about — forward to summarise a set, backward to hit a target. A test average that needs a certain last score is the same question a student meets for real.

How this one works

One question from this sheet, worked through a step at a time.

Missing number for a mean of 11

11 × 5=55
3 + 18 + 1 + 17 =39
55 − 39=16
  1. The mean is the total shared out evenly, so run it backward: 5 numbers with a mean of 11 must add up to 11 × 5 = 55.
  2. The numbers you already have add to 3 + 18 + 1 + 17 = 39.
  3. So the missing number is what is left to reach 55: 55 − 39 = 16.