三年级第25讲《速算与巧算》课后练习题答案
班级____________ 姓名____________
【共20☆,你得了( )☆】
用最简便的方法计算下面各题(每题1☆): (1)18+28+72
=18+100 =118
(2)454+232+768
=454+1000 =1454 (3)308+203-399+97
=203+97+308-399 =300+308-399 =608-400+1 =209
(4)1999+199+19
=2000+200+20-3 =2217
(5)282-49+718
=282+718-49 =951 (6)821-509+508
=821-1 =820 (7)41-64+29
=41+29-64 =6 (8)897+67
=900+64 =964
(9)877+345-677
=877-677+345 =545 (10)736-567+264 =1000-567 =433
(11)487+321+113+279 =487+113+(321+279) =600+600 =1200
(12)668-432+22+432 =668+22 =690
(13)832+71-833+70 =70+70 =140
(14)4+5+6+7+8+9+10+11+12+13
=(4+13)×(10÷2) =17×5 =85
(15)6+8+10+12+14+16+18+20
=(6+20)×(8÷2) =26×4 =104
(16)1+4+7+10+13+16+19+22+25 =26×4+13 =117
(17)15+20+25+30+35+40+45+50+55 =(15+55)×4+35 =70×4+35 =315
(18)53+49+51+48+52+50 =50×6+3 =303
(19)87+74+85+83+75+77+80+78+81+84 =800+7-6+5+3-5-3-2+1+4 =804
(20)1002+996+1004+995+998+1002 =6000+2-4+4-5-2+2 =5997