加法結(jié)合律

(a+b)+c=a+(b+c).例　有一批食品罐頭,標(biāo)準(zhǔn)質(zhì)量為每聽(tīng)454克.現(xiàn)抽取10聽(tīng)樣品進(jìn)行檢測(cè),結(jié)果如下表(單位:克).聽(tīng)號(hào)12345質(zhì)量444459454459454聽(tīng)號(hào)678910質(zhì)量454449454459464這10聽(tīng)罐頭的總質(zhì)量是多少?解　把超過(guò)標(biāo)準(zhǔn)質(zhì)量的克數(shù)用正數(shù)表示,不足的用負(fù)數(shù) ......    （本文共 338 字 ）     [閱讀本文] >>