能简便计算的要简便计算,并写出过程.①18.9-5.4-8.9②427×1129+2×4729×227③1999×19992000④12.5×3.2×25⑤10.8-(2.19+0.75÷25%)⑥625×[(512-316)×822].
能简便计算的要简便计算,并写出过程.
①18.9-5.4-8.9
②×+2××
③1999×
④12.5×3.2×25
⑤10.8-(2.19+0.75÷25%)
⑥×[(-)×].
答案和解析
①18.9-5.4-8.9
=18.9-8.9-5.4
=10-5.4
=4.6;
②
×+2××
=×+×
=×(+)
=×2
=;
③1999×
=(2000-1)×
=2000×-1×
=1999-
=1998;
④12.5×3.2×25
=12.5×(4×0.8)×25
=(12.5×0.8)×(4×25)
=10×100
=1000;
⑤10.8-(2.19+0.75÷25%)
=10.8-(2.19+3)
=10.8-5.19
=5.61;
⑥×[(-)×]
=×[×]
=×
=.
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