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Olympiad in the third grade of primary school: arithmetic progression calculation. 1、995+996+997+998+999。 (Calculation process)
1. Equation =1000x5-5-4-3-2-1= 4985.
2. Equation =1999-1998+1996+1995-1994 …+13-.
3. The nth item is 3n-2, so the sum of the first 100 items is 3x5050-200= 14950.
4.(94-25)/3+ 1=24 lines, so * * has (25+94)/2x24= 1428.