【答案】
(首項(xiàng)+末項(xiàng))×項(xiàng)數(shù)&pide;2=115項(xiàng)數(shù)是230(230=2×5×23)的約數(shù)。
⑴如果項(xiàng)數(shù)等于2,首項(xiàng)+末項(xiàng)=115,末項(xiàng)-首項(xiàng)=1答案為:57+58 ⑵如果項(xiàng)數(shù)等于5,首項(xiàng)+末項(xiàng)=46,末項(xiàng)-首項(xiàng)=4答案為21+22+23+24+25 ⑶如果項(xiàng)數(shù)等于10,首項(xiàng)+末項(xiàng)=23,末項(xiàng)-首項(xiàng)=9 答案為7+8+9+10+11+12+13+14+15+16 ⑷如果項(xiàng)數(shù)超過23,不可能,所以共有三種情況。



