Find the mean of two digit natural numbers which have both digits same

Options

A. 55
B. 45
C. 65
D. 50

Answer

To find the mean of two-digit natural numbers that have both digits the same, we can follow these steps:

### Step 1: Identify the two-digit natural numbers with both digits the same.
The two-digit natural numbers where both digits are the same are:
- 11
- 22
- 33
- 44
- 55
- 66
- 77
- 88
- 99

### Step 2: Count the number of observations.
We can count the numbers we have listed:
- There are 9 numbers: 11, 22, 33, 44, 55, 66, 77, 88, and 99.

### Step 3: Calculate the sum of these observations.
Now, we will add these numbers together:
- 11 + 22 + 33 + 44 + 55 + 66 + 77 + 88 + 99

Calculating the sum step by step:
- 11 + 22 = 33
- 33 + 33 = 66
- 66 + 44 = 110
- 110 + 55 = 165
- 165 + 66 = 231
- 231 + 77 = 308
- 308 + 88 = 396
- 396 + 99 = 495

So, the total sum is **495**.

### Step 4: Calculate the mean.
The mean is calculated by dividing the sum of the observations by the number of observations.

Mean = (Sum of observations) / (Number of observations)

Mean = 495 / 9

Calculating this gives:
- Mean = 55

### Final Answer:
The mean of the two-digit natural numbers with both digits the same is **55**.

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