《加、减法的简便运算》课本习题答案
P20 做一做
1、425+14+186 75+168+25
=425+(14+186) =75+25+168
=425+200 =100+168
=625 =268
245+180+20+155 67+25+33+75
=(245+155)+(25+75) =(67+33)+(25+75)
=400+200 =100+100
=600 =200
2、66+113+87+34=300(元)
P21 做一做
1、- 48 1500 + 415 - 74 + 26 a - b + c
2、528-53-47 545-167-145
=528-(53+47) =545-145-167
=528-100 =400-167
=428 =233
487-187-139-61 169-25-25-50
=(487-187)-(139+61) =169-(25+25+50)
=300-200 =169-100
=100 =69
P22-P23 练习六
1、60+255+40 282+41+159
=60+40+255 =282+(41+159)
=100+255 =282+200
=355 =482
548+52+468 800-138-162
=600+468 =800-(138+162)
=1068 =800-300
=500
672-36-64 672-36+64
=672-(36+64) =636+64
=672-100 =700
=572
13+46+55+54+87
=(13+87)+(46+54)+55
=100+100+55
=255
5+137+45+63+50
=(5+45+50)+(137+63)
=(50+50)+200
=300
2、255+328+175=225+175+328=728(元)
3、2000-416-284
=2000-(416+284)
=1300(m)
4、1+2+3+4+5+6+7+8+9+10=(1+10)×10÷2=55(根)
5、(从上到下)107 104 106 38
6、25
7、2255+355+245=2855(元)
8、(104-4)+(78-8)=170(名)
9、(1)1+2+3+4+…+98+99+100
=(1+100)×100÷2
=5050
(2)2+4+3+…+16+18+20
=(2+20)×10÷2
=110
(3)20-19+18-17+…+4-3+2-1
=(20-19)+(18-17)+…+(4-3)+(2-1)
=1+1+…+1+1
=1×10
=10