一小数的巧算（A）
年级班姓名得分
一、填空题
1．计算1.135+3.346+5.557+7.768+9.979=_____.
2.计算1.996+19.97+199.8=_____.
3.计算9.8+99.8+999.8+9999.8+99999.8=_____.
4.计算6.11+9.22+8.33+7.44+5.55+4.56+3.67+2.78+1.89=_____.
5.计算1.1+3.3+5.5+7.7+9.9+11.11+13.13+15.15+17.17+19.19=_____.
6.计算2.894.68+4.686.11+4.68=_____.
7.计算17.4837-17.4819+17.4882=_____.
8.计算1.250.322.5=_____.
9.计算754.7+15.925=_____.
10.计算28.6767+32286.7+573.40.05=_____.
二、解答题
11.计算172.46.2+27240.38
12.计算
13.计算12.34+23.45+34.56+45.67+56.78+67.89+78.91+89.12+91.23
14.下面有两个小数:求a+b,a-b,ab,ab.
一小数的巧算（B）
年级班姓名得分
一、真空题
1.计算4.75-9.64+8.25-1.36=_____.
2.计算3.17-2.74+4.7+5.29-0.26+6.3=_____.
3.计算(5.25+0.125+5.75)8=_____.
4.计算34.58.23-34.5+2.7734.5=_____.
5.计算6.250.16+2640.0625+5.26.25+0.62520=_____.
6.计算0.035935+0.035+30.035+0.07610.5=_____.
7.计算19.9837-199.81.9+19980.82=_____.
8.计算13.59.9+6.510.1=_____.
9.计算0.1250.250.564=_____.
10.计算11.8×43-860×0.09=_____.
二、解答题
11．计算32.14+64.28×0.5378×0.25+0.5378×64.28×0.75-8×64.28×0.125×0.5378.
12.计算0.888×125×73+999×3.
13.计算1998+199.8+19.98+1.998.
14.下面有两个小数:试求a+b,a-b,a×b,ab.
———————————————答案——————————————————————
1.27.785
2.221.766
原式=(2-0.004)+(20-0.03)+(200-0.2)
=222-(0.004+0.03+0.2)
=221.766
3.111109
提示:仿上题.
4.49.55
5.103.25
原式=1.1(1+3+…+9)+1.01(11+13+…+19)
=1.125+1.0175
=103.25
6.46.8
7.1748
原式=17.48×37-17.48×19+17.48×82
=17.48×(37-19+82)
=17.48×100
=1748
8.1
原式=(1.250.8)(0.42.5)
=11
=1
9.750
原式=754.7+5.3(325)
=75(4.7+5.3)
=7510
=750
10.2867
原式=28.6767+3228.67+28.67(200.05)
=28.67(67+32+1)
=28.67100
=2867
11.原式=172.46.2+(1724+1000)0.38
=172.46.2+17240.38+10000.38
=172.46.2+172.43.8+380
=172.4(6.2+3.8)+380
=172.410+380
=1724+380
=2104
12.181是三位,11是两位,相乘后18111=1991是四位,三位加两位是五位,因此1991前面还要添一个0,又963+1028=1991,所以
00…01810.00…011=0.00…01991
963个01028个01992个0
13.9个加数中,十位、个位、十分位、百分位的数都是1~9，所以原式=11.11(1+2+…+9)
=11.1145
=499.95
14.a是小数点后有(1994+3-1=)1996位的小数,b是小数点后有(1996+2-1=)1997位小数.
a+b=0.00…01069a-b=0.00…01031
1994个01994个0
ab=0.00…01995ab=105019=
3990个0
———————————————答案——————————————————————
1.2
原式=（4.75+8.25）-(9.64+1.36)
=13-11
=2
2.17
原式=(3.71+5.29)+(4.7+6.3)-(2.74+0.26)
=9+11-3
=17
3.89
原式=(5.25+5.75+0.125)8
=(11+0.125)8
=118+0.1258
=88+1
=89
4.345
原式=34.5(8.23+2.77-1)
=34.510
=345
5.62.5
原式=6.250.16+2.646.25+5.26.25+6.252
=6.25(0.16+2.64+5.2+2)
=6.2510
=62.5
6.35
7.1998
8.199.3
原式=13.5(10-0.1)+6.5(10+0.1)
=13.510-13.50.1+6.510+6.50.1
=135-1.35+65+0.65
=(135+65)-(1.35-0.65)
=200-0.7
=199.3
9.1
原式=0.1250.250.5(842)
=(0.1258)(0.254)(0.52)
=111
=1
10.430
原式=11.843-43200.09
=11.843-431.8
=43(11.8-1.8)
=4310
=430
11.
原式=32.14+64.280.5378(0.25+0.75-80.125)
=32.14+64.280.53780
=32.14
12.
原式=0.111(8125)73+111(93)
=11173+11127
=111(73+27)
=111100
=11100
13.
原式=(2000-2)+(200-0.2)+(20-0.02)+(2-0.002)
=2222-2.222
=2222-(10-7.778)
=2222-10+7.778
=2219.778
14.a+b,a的小数点后面有1998位,b的小数点后面有2000位,小数加法要求数位对齐,然后按整数的加法法则计算,所以
a+b=0.00…012508=0.00…012508
2000位1996个0
,方法与a+b一样,数位对齐,还要注意退位和补零,因为
a=0.00…0125，b=0.00…08,由12500-8=12492，所以
1998位2000位
a-b=0.00…12492=0.00…012492
2000位1996个0
ab,ab的小数点后面应该有1998+2000位,但1258=1000,所以
ab=0.00…01000=0.00…01
1998+2000位3995个0
ab,将a、b同时扩大100…0倍，得
2000个0
ab=125008=1562.5
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