**Finding the Mean:**

To find the mean of a set of numbers, we need to sum up all the numbers in the set and then divide the sum by the total number of elements in the set. In this case, we have a set of numbers in square units: 1 square, 2 square, 3 square, and 20 square. Let's calculate the mean step by step.

**Step 1: Calculate the Sum:**

First, we need to sum up all the numbers in the set. Adding 1 square, 2 square, 3 square, and 20 square, we get:

1 square + 2 square + 3 square + 20 square = 26 square

So, the sum of the numbers is 26 square.

**Step 2: Count the Elements:**

Next, we need to count the total number of elements in the set. In this case, we have 4 elements: 1 square, 2 square, 3 square, and 20 square.

**Step 3: Calculate the Mean:**

To find the mean, we divide the sum of the numbers by the total number of elements.

Mean = Sum of numbers / Total number of elements

Mean = 26 square / 4

Mean = 6.5 square

Therefore, the mean of the given set of numbers (1 square, 2 square, 3 square, and 20 square) is 6.5 square units.

In summary, to find the mean of a set of numbers, we sum up all the numbers and then divide the sum by the total number of elements in the set. In this case, the mean of the numbers 1 square, 2 square, 3 square, and 20 square is 6.5 square units.

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