题目内容
化简比并求比值. (1)12:30 |
(2)0.4:3.2 | (3)
|
分析:(1)根据比的基本性质,即比的前项和后项同时乘或除以一个相同的数(0除外)比值不变,进而把比化成最简比;
(2)根据求比值的方法,就用最简比的前项除以后项即得比值.
(2)根据求比值的方法,就用最简比的前项除以后项即得比值.
解答:解:(1)12:30,
=(12÷6):(30÷6),
=2:5;
12:30,
=2:5,
2÷5,
=
.
(2)0.4:3.2,
=(0.4×5):(3.2×5),
=2:16,
=1:8;
0.4:3.2,
=1:8,
=1÷8,
=
.
(3)
:
,
=(
×18):(
×18),
=12:5;
:
,
=12:5,
=12÷5,
=
.
=(12÷6):(30÷6),
=2:5;
12:30,
=2:5,
2÷5,
=
2 |
5 |
(2)0.4:3.2,
=(0.4×5):(3.2×5),
=2:16,
=1:8;
0.4:3.2,
=1:8,
=1÷8,
=
1 |
8 |
(3)
2 |
3 |
5 |
18 |
=(
2 |
3 |
5 |
18 |
=12:5;
2 |
3 |
5 |
18 |
=12:5,
=12÷5,
=
12 |
5 |
点评:此题考查化简比和求比值的方法,要注意区分:化简比的结果是一个比,它的前项和后项都是整数,并且是互质数;而求比值的结果是一个数,可以是整数、小数或分数.
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