一、口算。
$800÷5= $ $300÷15= $ $30×600= $
$46+123= $ $210×20= $ $600÷40= $
$600÷30= $ $1000÷50= $ $97-58= $
$14×300= $ $450+450= $ $144÷24= $
$720÷12= $ $600-60= $ $23+70= $
$300-124= $ $70×20= $ $305×2= $
$230+170= $ $106×5= $ $510÷30= $
$320-18= $ $360÷15= $ $410×20= $

160 20 18000 169 4200 15 20 20 39 4200 900 6 60 540 93 176 1400 610 400 530 17 302 24 8200

$800÷5=160$
$300÷15=20$
$30×600=18000$
$46+123=169$
$210×20=4200$
$600÷40=15$
$600÷30=20$
$1000÷50=20$
$97-58=39$
$14×300=4200$
$450+450=900$
$144÷24=6$
$720÷12=60$
$600-60=540$
$23+70=93$
$300-124=176$
$70×20=1400$
$305×2=610$
$230+170=400$
$106×5=530$
$510÷30=17$
$320-18=302$
$360÷15=24$
$410×20=8200$

二、计算下面各题,怎样简便就怎样计算。
$240-36×4÷18$ $572÷22×23-158$ $400×[(270+80)÷7]$
$3000÷125÷8$ $101×378-378$ $1600÷[2×(25+15)]$

232 440 20000 3 37800 20

1. $240 - 36×4÷18$
$\begin{aligned}&=240 - 144÷18\\&=240 - 8\\&=232\end{aligned}$
2. $572÷22×23 - 158$
$\begin{aligned}&=26×23 - 158\\&=598 - 158\\&=440\end{aligned}$
3. $400×[(270 + 80)÷7]$
$\begin{aligned}&=400×[350÷7]\\&=400×50\\&=20000\end{aligned}$
4. $3000÷125÷8$
$\begin{aligned}&=3000÷(125×8)\\&=3000÷1000\\&=3\end{aligned}$
5. $101×378 - 378$
$\begin{aligned}&=(101 - 1)×378\\&=100×378\\&=37800\end{aligned}$
6. $1600÷[2×(25 + 15)]$
$\begin{aligned}&=1600÷[2×40]\\&=1600÷80\\&=20\end{aligned}$