Question

14．工地上運(yùn)來(lái)沙土$\begin{array}{l}\frac{12}{5}\end{array}$噸，運(yùn)來(lái)的石子是沙土的$\begin{array}{l}\frac{7}{6}\end{array}$，又是石灰的$\begin{array}{l}\frac{14}{15}\end{array}$，工地運(yùn)來(lái)石灰多少?lài)崳?

Answer 1

分析 工地上運(yùn)來(lái)沙土$\begin{array}{l}\frac{12}{5}\end{array}$噸，運(yùn)來(lái)的石子是沙土的$\begin{array}{l}\frac{7}{6}\end{array}$，將沙土噸數(shù)當(dāng)作單位“1”，根據(jù)分?jǐn)?shù)乘法的意義，運(yùn)來(lái)石子$\begin{array}{l}\frac{12}{5}\end{array}$×$\begin{array}{l}\frac{7}{6}\end{array}$噸，又運(yùn)來(lái)石子是石灰的$\begin{array}{l}\frac{14}{15}\end{array}$，將石灰噸數(shù)當(dāng)作單位“1”，根據(jù)分?jǐn)?shù)除法的意義，用石子噸數(shù)除以其占石灰噸數(shù)的分率，即得工地運(yùn)來(lái)石灰多少?lài)崳?/p>

解答 解：$\begin{array}{l}\frac{12}{5}\end{array}$×$\begin{array}{l}\frac{7}{6}\end{array}$÷$\begin{array}{l}\frac{14}{15}\end{array}$
=$\frac{14}{5}$$÷\frac{14}{15}$
=3（噸）
答：工地運(yùn)來(lái)石灰3噸．

點(diǎn)評(píng) 求一個(gè)數(shù)的幾分之幾是多少，用乘法計(jì)算，已知一個(gè)數(shù)的幾分之幾是多少，求這個(gè)數(shù)，用除法計(jì)算．