题目内容
比一比,看谁算得快! 1039-(539+78)= |
78+79+80+81+84+77+75= |
1-2+3-4+5-6+7-8+9-10+11-12+13= |
1+11+101+1001= |
159-55-45= |
162-55-62= |
79+68+21= |
4×25= |
16×125= |
8×9+10= |
42÷7= |
分析:(1)运用减法的性质简算;
(2)每个数都在80左右,因此把原式化为(80-2)+(80-1)+80+(80+1)+(80+4)+(80-3)+(80-5),计算即可;
(3)从后向前,每两个数为一组,每组得数为1,计算即可;
(4)把原式化为1+(10+1)+(100+1)+(1000+1),计算即可;
(5)运用减法的性质简算;
(6)、(7)运用加法交换律简算;
(8)、(11)直接写出答案即可;
(9)把16看做2×8,运用乘法结合律简算;
(10)先算乘法,再算加法.
(2)每个数都在80左右,因此把原式化为(80-2)+(80-1)+80+(80+1)+(80+4)+(80-3)+(80-5),计算即可;
(3)从后向前,每两个数为一组,每组得数为1,计算即可;
(4)把原式化为1+(10+1)+(100+1)+(1000+1),计算即可;
(5)运用减法的性质简算;
(6)、(7)运用加法交换律简算;
(8)、(11)直接写出答案即可;
(9)把16看做2×8,运用乘法结合律简算;
(10)先算乘法,再算加法.
解答:解:(1)1039-(539+78),
=1039-539-78,
=500-78,
=422;
(2)78+79+80+81+84+77+75,
=(80-2)+(80-1)+80+(80+1)+(80+4)+(80-3)+(80-5),
=80×7-(2+1-1-4+3+5),
=560-6,
=554;
(3)1-2+3-4+5-6+7-8+9-10+11-12+13,
=(13-12)+(11-10)+(9-8)+(7-6)+(5-4)+(3-2)+1,
=7;
(4)1+11+101+1001,
=1+(10+1)+(100+1)+(1000+1),
=1110+4,
=1114;
(5)159-55-45,
=159-(55+45),
=159-100,
=59;
(6)162-55-62,
=162-62-55,
=100-55,
=45;
(7)79+68+21,
=79+21+68,
=100+68,
=168;
(8)4×25=100;
(9)16×125,
=2×8×125,
=2×(8×125),
=2×1000,
=2000;
(10)8×9+10,
=72+10,
=82;
(11)42÷7=6.
故答案为:422,554,7,1114,59,45,168,100,2000,82,6.
=1039-539-78,
=500-78,
=422;
(2)78+79+80+81+84+77+75,
=(80-2)+(80-1)+80+(80+1)+(80+4)+(80-3)+(80-5),
=80×7-(2+1-1-4+3+5),
=560-6,
=554;
(3)1-2+3-4+5-6+7-8+9-10+11-12+13,
=(13-12)+(11-10)+(9-8)+(7-6)+(5-4)+(3-2)+1,
=7;
(4)1+11+101+1001,
=1+(10+1)+(100+1)+(1000+1),
=1110+4,
=1114;
(5)159-55-45,
=159-(55+45),
=159-100,
=59;
(6)162-55-62,
=162-62-55,
=100-55,
=45;
(7)79+68+21,
=79+21+68,
=100+68,
=168;
(8)4×25=100;
(9)16×125,
=2×8×125,
=2×(8×125),
=2×1000,
=2000;
(10)8×9+10,
=72+10,
=82;
(11)42÷7=6.
故答案为:422,554,7,1114,59,45,168,100,2000,82,6.
点评:此题考查了学生运用运算定律或性质简算的能力,以及对四则混合运算顺序的掌握情况.
练习册系列答案
相关题目