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What is the sum of the first 100 counting numbers?

Published in Sum of Numbers 1 min read

The sum of the first 100 counting numbers (1 to 100) is 5050.

Calculating the Sum

We can calculate the sum of the first 100 counting numbers using a formula. According to the provided reference, the formula for the sum of natural numbers is:

S = n/2 [2a + (n − 1) × d]

Where:

  • S = Sum of the numbers
  • n = Number of terms (in this case, 100)
  • a = First term (in this case, 1)
  • d = Common difference (in this case, 1)

Applying these values, we get:

S = 100/2 [2(1) + (100 - 1) × 1]
S = 50 [2 + 99]
S = 50 [101]
S = 5050

Formula Application

The formula used is a generalized version for arithmetic series, but a simplified formula exists specifically for the sum of the first 'n' natural numbers:

S = n(n+1)/2

For n = 100:

S = 100(100+1)/2
S = 100(101)/2
S = 10100/2
S = 5050

Example

Let's illustrate the concept with a smaller set. What is the sum of the first 10 counting numbers?

  • n = 10
    S = 10(10+1)/2
    S = 10(11)/2
    S = 110/2
    S = 55

Therefore, 1 + 2 + 3 + 4 + 5 + 6 + 7 + 8 + 9 + 10 = 55

Summary

Detail Value
Sum of first 100 numbers 5050
Formula Used S = n(n+1)/2
Number of terms (n) 100

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