| 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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