Question

19．梨樹(shù)的棵數(shù)比桃樹(shù)多$\frac{2}{7}$，桃樹(shù)的棵數(shù)比梨樹(shù)少$\frac{2}{7}$．×．（判斷對(duì)錯(cuò)）

Answer 1

分析 梨樹(shù)的棵數(shù)比桃樹(shù)多$\frac{2}{7}$，是把桃樹(shù)的棵數(shù)看作單位“1”，梨樹(shù)的棵數(shù)就是（1+$\frac{2}{7}$），求桃樹(shù)比梨樹(shù)少幾分之幾，就是求桃樹(shù)比梨樹(shù)少的棵數(shù)占梨樹(shù)棵數(shù)的幾分之幾，用桃樹(shù)比梨樹(shù)少的棵數(shù)除以梨樹(shù)的棵數(shù)．

解答 解：（1+$\frac{2}{7}$-1）÷（1+$\frac{1}{7}$）
=$\frac{2}{7}$÷$\frac{9}{7}$
=$\frac{2}{9}$
即梨樹(shù)的棵樹(shù)比桃樹(shù)多$\frac{2}{7}$，桃樹(shù)的棵樹(shù)比梨樹(shù)少$\frac{2}{9}$．
故答案為：×．

點(diǎn)評(píng) 把桃樹(shù)的棵數(shù)看作單位“1”，把它平均分成7份，梨樹(shù)的棵數(shù)多這樣的2份，相當(dāng)于這樣的9份，桃樹(shù)比梨樹(shù)少2份，這2份就是梨樹(shù)的$\frac{2}{9}$．