题目内容
脱式计算. 6.5×8+3.5×8-44 | 8.5+(5.6-4.8)×13 | 1.9-1.9×(1.9-1.9) |
×29+×29+29 | 1×÷× | ×101- |
49.5×-(50-)×0.6 | ×+÷+ | ÷[×(1-)] |
897×-37.5%+104×0.375 | [+×(-0.375)]÷ | ++++ |
-(+) |
解:
(1)6.5×8+3.5×8-44,
=(6.5+3.5)×8-44,
=10×8-44,
=80-44,
=36;
(2)8.5+(5.6-4.8)×13,
=8.5+0.8×13, =8.5+10.4, =18.9; (3)1.9-1.9×(1.9-1.9), =1.9-1.9×0, =1.9-0, =1.9; (4)×29+×29+29 =(++1)×29, =2×29, =58; (5)1×÷×, =×2000×, =20×, =2; (6)×101-, =(101-1)×, =100×, =28; (7)49.5×-(50-)×0.6, =49.5×10.6-49.5×0.6, =49.5×(10.6-0.6), =49.5×10, =495; (8)×+÷+, =×+×+, =(++1)×, =11×, =7; (9)÷[×(1-)], =÷[×], =÷, =×, =; (10)897×-37.5%+104×0.375, =897×0.375-0.375+104×0.375, =(897-1+104)×0.375, =1000×0.375, =375; (11)[+×(-0.375)]÷, =[+×(-)]÷, =[+×]÷, =[+]÷, =×, =; (12)++++, =(9+99+999+9999)+×5, =9+99+999+9999+4, =(9+1)+(99+1)+(999+1)+(9999+1), =10+100+1000+10000, =11110; (13)-(+), =--, =2-, =. |
分析:
(1)先根据四则混合运算的顺序确定应该先算什么后算什么:只有一级运算时,从左到右计算;有两级运算时,先算乘除,后算加减.有一层括号时,先算括号里的;有多层括号时,先算小括号里的. (2)能够运用简便算法的题目,根据所学定律选择适合的简便方法. |
点评:此题主要考察四则混合运算的顺序和简便算法的灵活运用,要根据每一题的特点选择适合的方法.
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