Method 1 (Sum of the first n numbers): The sum of the first n positive integers is n(1 + n)/2 So the sum would be 1,000,000 * (1,000,001)/2 = 500,000,500,000. Method 2 (Algebraic Solution): Let x be the sum of the numbers 1 through 1,000,000. x = 1 + 2 + ... + 999,999 + 1,000,000. x = 1,000,000 + 999,999 + ... + 2 + 1 Adding these equations gives: 2x = 1,000,001 + 1,000,001 + ... + 1,000,001 + 1,000,001 Note that there are 1,000,000 different 1,000,001's in the above equation. So: 2x = 1,000,001(1,000,000) = 1,000,001,000,000 x = 500,000,500,000.
The sum of the first 1,000,000 positive even numbers is: 2 + 4 + 6 + 8 + ... + 2,000,000 The sum of the first 1,000,000 positive odd integers is: 1 + 3 + 5 + 7 + ... + 1,999,999 The difference between the two is: (2-1) + (4-3) + (6-5) + (8-7) + ... + (2,000,000-1,999,999). This is the same as: 1 + 1 + 1 + 1 + ... + 1. Well how many 1's are there? 1,000,000. So the difference is 1,000,000. Note that if the question asked for the difference between the sum of the first 1,000 positive even numbers and the sum of the first 1,000 positive odd numbers, the answer would be 1,000. The first n even numbers and odd numbers? n.
3,5,7,8
1
The numbers 32 and 1 (32 x 1 = 32) sum to 33. The numbers 4 and 8 (4 x 8 = 32) sum to 12 The numbers 2 and 16 (2 x 16 = 32) sum to 18. There are no other factors which are integers, so 32 and 1 is the answer.
The two numbers are 5 and -6. 5x(-6) = -30 so the product is -30 and 5+(-6) = -1 so the sum is -1
The sum of the numbers 1 through 27 is 378.
The sum of the numbers from 1 through 100 is 5,050.
The sum of all the numbers 1 through 200 is 20,100.
If you count from 1 to 1000000 you count 1000000 numbers so there are 1000000 numbers in 1000000
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 whole numbers 1 through 30 is 465.
201
The sum of all the odd numbers from 1 through 100 is 10,000
465
28
2,850