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Question

What is the mean of first hundred natural numbers?

This question was previously asked in
RRB ALP 2018 CBT 2 Fitter Question Paper (21-Jan-2019) (Shift 3)
The correct answer is

50.5

Finding the Mean of the First Hundred Natural Numbers

The question asks for the mean of the first hundred natural numbers. Let's break down how to solve this problem.

Understanding Natural Numbers

Natural numbers are the counting numbers starting from 1. The first hundred natural numbers are 1, 2, 3, ..., all the way up to 100.

So, the list of numbers is: 1, 2, 3, 4, ..., 99, 100.

What is the Mean?

The mean, also known as the arithmetic average, is calculated by summing up all the numbers in a set and then dividing by the total count of numbers in that set.

The formula for the mean is:

\( \text{Mean} = \frac{\text{Sum of all numbers}}{\text{Total count of numbers}} \)

Calculating the Sum of the First Hundred Natural Numbers

To find the sum of the first 'n' natural numbers, there's a handy formula:

\( \text{Sum} = \frac{n(n+1)}{2} \)

In this case, we are dealing with the first hundred natural numbers, so \(n = 100\).

Let's plug \(n=100\) into the formula:

\( \text{Sum} = \frac{100(100+1)}{2} \)

\( \text{Sum} = \frac{100(101)}{2} \)

\( \text{Sum} = \frac{10100}{2} \)

\( \text{Sum} = 5050 \)

So, the sum of the first hundred natural numbers is 5050.

Determining the Total Count of Numbers

We are considering the first hundred natural numbers. This means there are exactly 100 numbers in our set.

\( \text{Total count of numbers} = 100 \)

Calculating the Mean

Now we have the sum (5050) and the count (100). We can use the mean formula:

\( \text{Mean} = \frac{\text{Sum of all numbers}}{\text{Total count of numbers}} \)

\( \text{Mean} = \frac{5050}{100} \)

\( \text{Mean} = 50.5 \)

Thus, the mean of the first hundred natural numbers is 50.5.

Step Description Value
1 Identify 'n' (number of natural numbers) 100
2 Calculate the sum using the formula \( \frac{n(n+1)}{2} \) \( \frac{100(101)}{2} = 5050 \)
3 Identify the total count of numbers 100
4 Calculate the mean using \( \frac{\text{Sum}}{\text{Count}} \) \( \frac{5050}{100} = 50.5 \)

The calculated mean is 50.5.

Revision Table: Mean of First Hundred Natural Numbers

Concept Definition/Formula
Natural Numbers Counting numbers starting from 1 (1, 2, 3, ...)
Mean (Arithmetic Average) \( \frac{\text{Sum of observations}}{\text{Number of observations}} \)
Sum of first 'n' Natural Numbers \( \frac{n(n+1)}{2} \)

Additional Information: Properties of Natural Numbers and Mean

Natural numbers form the basis of many mathematical concepts. The set of natural numbers is often denoted by \( \mathbb{N} = \{1, 2, 3, \dots\} \).

The mean is a measure of central tendency, giving us a typical value for a dataset. Other measures of central tendency include the median (the middle value) and the mode (the most frequent value).

The formula for the sum of the first 'n' natural numbers was discovered by the mathematician Carl Friedrich Gauss. This formula is very useful for quickly summing arithmetic progressions where the first term is 1 and the common difference is 1.

In this case, the numbers form an arithmetic progression with the first term \(a_1 = 1\) and the last term \(a_{100} = 100\). The mean of an arithmetic progression is simply the average of the first and last terms:

\( \text{Mean} = \frac{a_1 + a_n}{2} = \frac{1 + 100}{2} = \frac{101}{2} = 50.5 \)

This confirms our earlier calculation using the sum formula.

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Similar Questions

  1. The mean of the 5 smallest numbers from a group is 15 while the mean of all the numbers of the group taken together is 17. If the mean of the numbers leaving the smallest five out is 18.25, how many numbers were there in the group in all?

  2. The total weight of school bags of 35 students of a class was 449.75 kg. What is the average weight of each school bag if each student carried only one school bag?

  3. The mean of three numbers is 15. The range of this data set is 8 while the difference between the two smallest numbers is 1. The greatest of the three numbers is:
  4. The mean height of 25 boys in a class is 150 cm, and the mean height of 35 girls in the same class is 145 cm. The combined mean height of 60 students in the class is ______ cm (approximately).

  5. Four numbers, when arranged in ascending order, are w, x, y and z. The average of the smallest three numbers is 18, while the average of the largest three was 22. What is the range of the data?

  6. Samit was given some money to take care of his travel during a 6-day sales drive he had to undertake. However, he had to increase his stay by another 4 days and as a result his average daily travel allowance went down by Rs. 56. What was the amount that was sanctioned to him in the beginning?

  7. The average of three numbers is 6. The average of the first two is 5 while the average of the last two is 8. The three numbers are:

  8. The average marks obtained by Raghav in 15 tests are 25. Zubeida has maintained an average of 23 so far but has taken only 10 of the tests. If each test is out of 30, how much must Zubeida score on average in the remaining 5 tests to still have a chance to match Raghav’s performance?

  9. What is the mean of first 60 natural numbers?

  10. The average marks obtained by Raghav in 12 tests is 24. Zubeida has maintained an average of 23 so far but has taken only 9 of the tests. If each test is out of 30, at least how much must Zubeida score in any one of the remaining three tests to still have a chance to match Raghav’s performance?


Important Questions from Average

  1. Average of 40 numbers is 71, if the number 100 replaced by 140, then average is increased by

  2. The captain of a football team of 11 members is 28 years old and the goalkeeper is 4 years older than him. If the ages of these two are removed, then the average age of the remaining players is two years less than the average age of the whole team. What is the average age of the team?

  3. There are two Classes A and B having 25 and 30 students respectively. In Class-A the highest score is 21 and lowest score is 17. In Class-B the highest score is 30 and lowest score is 22. Four students are shifted from Class-A to Class-B.

    Consider the following statements:

    1. The average score of Class-B will definitely decrease.

    2. The average score of Class-A will definitely increase.

    Which of the above statements is/are correct?

  4. The average weight of A, B, Cis 40 kg, the average weight of B, D, Eis 42 kg and the weight of Fis equal to that of B. What is the average weight of A, B, C, D, Eand F?

  5. A cow costs more than 4 goats but less than 5 goats. If a goat costs between Rs. 600 and Rs. 800, which of the following is a most valid conclusion?

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