Question

17．果園里有蘋(píng)果樹(shù)、梨樹(shù)和桔樹(shù)共400棵．蘋(píng)果樹(shù)的棵數(shù)是另外兩種樹(shù)棵數(shù)的$\frac{1}{4}$，梨樹(shù)棵數(shù)是蘋(píng)果樹(shù)棵數(shù)的20%．果園的三種樹(shù)各有多少棵？

Answer 1

分析 已知蘋(píng)果樹(shù)的棵數(shù)是另外兩種樹(shù)棵數(shù)的$\frac{1}{4}$，也就是蘋(píng)果樹(shù)的棵數(shù)占總數(shù)$\frac{1}{1+4}$，把總數(shù)看作單位“1”，根據(jù)一個(gè)數(shù)乘分?jǐn)?shù)的意義，用乘法即可求出蘋(píng)果樹(shù)的棵數(shù)．又知梨樹(shù)棵數(shù)是蘋(píng)果樹(shù)棵數(shù)的20%，再把蘋(píng)果樹(shù)的棵數(shù)看作單位“1”，根據(jù)一個(gè)數(shù)乘分?jǐn)?shù)的意義，即可求出梨樹(shù)的棵數(shù)，然后用三種樹(shù)總棵數(shù)減去蘋(píng)果樹(shù)、梨樹(shù)的棵數(shù)就是桔樹(shù)的棵數(shù)．

解答 解：400×$\frac{1}{1+4}$
=$400×\frac{1}{5}$
=80（棵）；

80×20%
=80×0.2
=16（棵）；

400-80-16
=320-16
=304（棵）；
答：果園有蘋(píng)果樹(shù)80棵、梨樹(shù)16棵、桔樹(shù)304棵．

點(diǎn)評(píng) 此題解答關(guān)鍵是確定單位“1”，重點(diǎn)是求出蘋(píng)果樹(shù)的棵數(shù)占總數(shù)的幾分之幾，根據(jù)一個(gè)數(shù)乘分?jǐn)?shù)的意義求出蘋(píng)果樹(shù)的棵數(shù)，進(jìn)而求出梨樹(shù)、桔樹(shù)的棵數(shù)．