第1个回答 2013-07-21
315×77×13
=315×(77×13)
=315×1001
=315×(1000+1)
=315×1000+315
=315000+315
=315315
67×31+31×85+152×69
=31×(67+85)+152×69
=31×152+152×69
=152×(31+69)
=152×100
=15200
79×8181-81×7979 ………变一变 就简便
=79×81×101-81×79×101
=0
6666×6666 ………变一变 就简便
=(3333×2)×(3×2222)
=(3333×3)×(2×2222)
=9999×4444
=(10000-1)×4444
=44440000-4444
=44435556
15×213÷27+15×327÷27
=15×(213+327)÷27
=15×(540÷27)
=15×20
=300
1+2-3+4+5-6+7+8-9+……+97+98-99
分组计算:
1+2-3=0;
4+5-6=3;
7+8-9=6;
10+11-12=9;
……………………
97+98-99=96。
1+2-3+4+5-6+7+8-9+……+97+98-99
=0+3+6+9+……+96
=(0+96)×(99÷3)÷2
=1584
999×222+333×334 ………把999写成333×3
=333×3×222+333×334
=333×666+333×334
=333×(666+334)
=333×1000
=333000
164×166-163×167
=(163+1)×166-163×(166+1)
=163×166+166-163×166-163
=166-163
=3
19941994×1995-19951995×1994
=1994×10001×1995-1995×10001×1994
=0
66…… 6×99…… 9的积是多少? 66…… 6=100个6 99…… 9=100个9
=66…… 6×(100…… 00-1) 有100个0
=66…6100……0-66… 6 100个6,100个0。
=66…6033……34 100个6,99个3,
1+2-3-4+5+6-7-8+9+10-……+1990
分组计算:
1
+2-3=-1
-4+5=1
+6-7=-1
-8+9=1
+10-11=-1
…………………… 有995对数,其中正1有498个,负1有487个
-1989+1990=1
1+2-3-4+5+6-7-8+9+10-……+1990
=1×498-1×497
=498-497
=1
76000÷1 00……0×2 00……0 (00……0=100个0 00……0=98个0)
=7600……0(有97个0)×200……0(有98个0)
=15200……0(有195个0)
243×247-242×248
=(242+1)×247-242×(247+1)
=242×237+247-242×247-242
=247-242
=5
第2个回答 2013-07-22
315 X 77 X 13
= 315 X 11 X 7 X 13
= 315 X 11 X 91
= 315 X 1001
= 315315
67 X 31 + 31 X 85 + 152 X 69
= 32 X (67 + 85) + 152 X 69
= 32 X 152 + 152 X 69
= 152 X (32 + 69)
= 152 X 101
= 15352
79 X 8181 - 81 X 7979
= 79 X 81 X 101 - 81 X 79 X 101
= 0
6666 X 6666
= 2 X 3333 X 3333 X 2
= 4 X 9999 X 1111
= 4444 X (10000 - 1)
= 4444 0000 - 4444
= 4443 5556
15 X 213 / 27 + 15 X 327 / 27
= ( 213 + 327 ) X 15 / 27
= 540 X 5 / 9
= 60 X 5
= 300
1+2 -3 + 4+5 -6 + 7+8 -9 +……+ 97+98 -99
= 1-1 + 4-1 + 7-1 +……+ 97-1
= 0 + 3 + 6 +……+ 96
= 3 X ( 1 +2 +3 +……+ 32 )
= 3 X 32 X 33 / 2
= 99 X 16
= 1600 - 16
= 1584
999 X 222 + 333 X 334
= 333 X 666 + 333 X 334
= 333 X ( 666 + 334 )
= 333 X 1000
= 333000
164 X 166 - 163 X 167
= (165 - 1)(165 + 1) - (165 - 2)(165 + 2)
= ( 165" - 1" ) - ( 165" - 2" )
= 165" - 1 - 165" + 4
= 4 - 1
= 3
19941994 X 1995 - 19951995 X 1994
= 10001 X 1994 X 1995 - 10001 X 1995 X 1994
= 0
1 +2 -3 -4 +5 +6 -7 -8 +9 +10 +……+ 1990
= 1+ (2-3-4+5) +(6-7-8+9) +10 +……+ (1986-1987-1988+1989) +1990
= 1 + 0 + 0 +……+ 0 + 1990
= 1991
76000 / 1000……00 X 20……00
= 76000 X 20……00 / 1000……00
= 760 X 2000……00 / 1000……00
= 760 X 2
= 1520
243 X 247 - 242 X 248
= (245 - 2)(245 + 2) - (245 - 3)(245 + 3)
= ( 245" - 2" ) - ( 245" - 3" )
= 245" - 4 - 245" + 9
= 9 - 4
= 5
第3个回答 2013-08-04
解:315×77×13
=315×(7×11×13)
=315×1001
=315315
67×31+31×85+152×69
=31×(67+85)+152×69
=31×152+152×69
=152×(31+69)
=152×100
=15200