The sum of the numbers from 1 through 100 is 5,050.
The sum of all the numbers 1 through 200 is 20,100.
The sum of the whole numbers 1 through 1,000 is 500,500.
The sum of all odd numbers 1 through 99 is 9,801.
The sum of the even numbers is (26 + 28 + ... + 100); The sum of the odd numbers is (25 + 27 + ... + 99) Their difference is: (26 + 28 + ... + 100) - (25 + 27 + ... + 99) = (26 - 25) + (28 - 27) + ... + (100 - 99) = 1 + 1 + ... + 1 There are (100 - 26) ÷ 2 + 1 = 38 terms above which are all 1; their sum is 38 x 1 = 38. So the difference of the sum of all even numbers and all odd numbers 25-100 is 38.
The sum of the numbers from 1 through 100 is 5,050.
The sum of all the numbers 1 through 200 is 20,100.
The sum of the whole numbers 1 through 1,000 is 500,500.
The sum of all odd numbers 1 through 99 is 9,801.
Let the second number be x, then the three consecutive numbers are x-1, x, x+1, and their sum is: (x-1) + x + (x+1) = 81 3x = 81 x = 27 So the three numbers are 27-1, 27, 27+1 = 26, 27, 28
The sum of whole numbers 1 through 30 is 465.
201
The sum of the even numbers is (26 + 28 + ... + 100); The sum of the odd numbers is (25 + 27 + ... + 99) Their difference is: (26 + 28 + ... + 100) - (25 + 27 + ... + 99) = (26 - 25) + (28 - 27) + ... + (100 - 99) = 1 + 1 + ... + 1 There are (100 - 26) ÷ 2 + 1 = 38 terms above which are all 1; their sum is 38 x 1 = 38. So the difference of the sum of all even numbers and all odd numbers 25-100 is 38.
The sum of all the odd numbers from 1 through 100 is 10,000
465
28
2,850