Eddie's Football Card
Algebra
Level
2
Eddie gave me a football card at supper. If He gave me 2 cards tomorrow, 3 cards the day after tomorrow and so on, how many cards would I have after 100 days? (today is the first day.)
The answer is 5050.
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This is a Gauss sum,because we are suming consecutive terms. The formula is 1+2+3+...+(n-2)+(n-1)+n=n (n+1)/2. Pluging in n=100,we get 1+2+3+...+98+99+100=100 101/2=50*101=5050 cards.