解:(1)4.2:
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,
=(4.2×4):(
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×4),
=16.8:7,
=(16.8×10):(7×10),
=168:70,
=(168÷14):(70÷14),
=12:5;
(2)120:72,
=(120÷24):(70÷24),
=5:3;
(3)
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:
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:
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,
=(
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×147):(
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×147):(
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×147),
=21:3:49;
(4)36分:1小時(shí),
=36分:(1小時(shí)×60),
=36:60,
=3:5;
(5)308立方厘米:2立方分米,
=308立方厘米:(2立方分米×1000),
=308:2000,
=(308÷4):(2000÷4),
=77:500;
(6)1平方米:4320平方厘米,
=(1平方米×10000):4320平方厘米,
=10000:4320,
=(10000÷80):(4320÷80),
=125:54.
分析:根據(jù)比的基本性質(zhì)作答,即比的前項(xiàng)和后項(xiàng)同時(shí)乘或除以一個(gè)數(shù)(0除外)比值不變.
點(diǎn)評(píng):此題主要考查了化簡(jiǎn)比的方法,另外還要注意化簡(jiǎn)比的結(jié)果是一個(gè)比,它的前項(xiàng)和后項(xiàng)都是整數(shù),并且是互質(zhì)數(shù).