Question

1．甲數(shù)是乙數(shù)的1.25倍，甲數(shù)是乙數(shù)的$\frac{5}{4}$，乙數(shù)是甲、乙兩數(shù)和的$\frac{4}{9}$．

Answer 1

分析 把乙數(shù)看作單位“1”，則甲數(shù)就是1.25，化成分?jǐn)?shù)就是$\frac{5}{4}$，求甲數(shù)是乙的幾分之幾，用甲數(shù)除以乙數(shù)；求乙數(shù)是甲、乙兩數(shù)的幾分之幾，用乙數(shù)除以甲、乙兩數(shù)的和．

解答 解：設(shè)乙為“1”，則甲數(shù)是1×1.25=1.25=$\frac{5}{4}$．
$\frac{5}{4}$÷1=$\frac{5}{4}$
1÷（1+$\frac{5}{4}$）
=1÷$\frac{9}{4}$
=$\frac{4}{9}$
即甲數(shù)是乙數(shù)的1.25倍，甲數(shù)是乙數(shù)的$\frac{5}{4}$，乙數(shù)是甲、乙兩數(shù)和的$\frac{4}{9}$．
故答案為：$\frac{5}{4}$，$\frac{4}{9}$．

點評 求一個數(shù)是另一個數(shù)的幾分之幾，用這個數(shù)除以另一個數(shù)．解答此題的關(guān)鍵根據(jù)題意設(shè)乙為“1”，求出乙數(shù)．