1公里== 1千米==1000米 1噸== 1千克==1000克1米==10分米==100厘米==1000毫米

和==(首項(xiàng)+末項(xiàng))×項(xiàng)數(shù)÷2 鋸的次數(shù)比段數(shù)少1.

項(xiàng)數(shù)==(末項(xiàng)—首項(xiàng))÷公差+1 樓(段)數(shù)比層數(shù)少1.

末項(xiàng)==公差×(項(xiàng)數(shù)—1)+首項(xiàng)