一、用简便方法计算。
$125×32$
$720÷15÷6$
$125×25×8×4$
$250×16$
$498 - 154 - 46$
$29 + 65 + 71 + 35$
$105 + 336 + 164$
$56×103 - 56×3$
$20×74×50$
$401×70$
$35×23 + 35×37$
$175×23 - 75×23$
$28×45×20$
$78×201 - 78$
$429 - (55 + 29) - 145$

1. $125×32$
解：$125×32 = 125×8×4 = 1000×4 = 4000$
2. $720÷15÷6$
解：$720÷15÷6 = 720÷(15×6) = 720÷90 = 8$
3. $125×25×8×4$
解：$125×25×8×4=(125×8)×(25×4)=1000×100 = 100000$
4. $250×16$
解：$250×16 = 250×4×4 = 1000×4 = 4000$
5. $498 - 154 - 46$
解：$498 - 154 - 46 = 498-(154 + 46)=498 - 200 = 298$
6. $29 + 65 + 71 + 35$
解：$29 + 65 + 71 + 35=(29 + 71)+(65 + 35)=100 + 100 = 200$
7. $105 + 336 + 164$
解：$105 + 336 + 164 = 105+(336 + 164)=105 + 500 = 605$
8. $56×103 - 56×3$
解：$56×103 - 56×3 = 56×(103 - 3)=56×100 = 5600$
9. $20×74×50$
解：$20×74×50=(20×50)×74 = 1000×74 = 74000$
10. $401×70$
解：$401×70=(400 + 1)×70 = 400×70+1×70 = 28000 + 70 = 28070$
11. $35×23 + 35×37$
解：$35×23 + 35×37 = 35×(23 + 37)=35×60 = 2100$
12. $175×23 - 75×23$
解：$175×23 - 75×23=(175 - 75)×23 = 100×23 = 2300$
13. $28×45×20$
解：$28×45×20 = 28×(45×20)=28×900 = 25200$
14. $78×201 - 78$
解：$78×201 - 78 = 78×(201 - 1)=78×200 = 15600$
15. $429-(55 + 29)-145$
解：$429-(55 + 29)-145=(429 - 29)-(55 + 145)=400 - 200 = 200$