While calculating the average of 1st 3 positive numbers , one number was missed out and the average of remaining numbers was found to be 9 . Find the missing number

Let's denote the first three positive numbers as \(1, 2, 3\).

The sum of these numbers is:
\[
1 + 2 + 3 = 6
\]

Now, it's given that one of these numbers was missed, and the average of the remaining two numbers is 9. Let the missing number be \( x \).

The sum of the remaining two numbers (after missing one) is:
\[
1 + 2 + 3 - x = 6 - x
\]

The average of the two remaining numbers is given as 9, so we can set up the equation for the average:
\[
\frac{6 - x}{2} = 9
\]

Multiplying both sides of the equation by 2:
\[
6 - x = 18
\]

Solving for \( x \):
\[
x = 6 - 18 = -12
\]

Therefore, the missing number is \( -12 \).

Would you like further clarification on any part of the solution, or need help with additional questions?

Here are 5 related questions for practice:
1. What is the average of the first 5 positive numbers?
2. If the average of 3 numbers is 10, what is their total sum?
3. How would the average change if a number larger than 3 is added to the first three positive numbers?
4. What is the sum of the first 100 positive integers?
5. How do you find the median of a set of numbers?

**Tip:** Always check the problem carefully for clues on how many numbers are being averaged or missed, as it affects how you set up the equation.

While calculating the average of 1st 3 positive numbers, one number was missed out and the average of remaining numbers was found to be 9. Find the missing number.

Learn how to find a missing number when calculating the average of the first three positive numbers. This problem uses algebraic concepts and equation solving, suitable for students in Grades 6-8. The solution involves determining the average after one number is missed and solving for the unknown value.

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