巧算12*125 9
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12*14/2+14*16/2+16*18/2+18*20/2+20/1=1/12-1/14+1/14-1/16+1/16-1/18+1/18-1/20+1/20=1/12(即12分之1)
原式等于:(5/6-7/12)+(9/20-11/30)+13/42=(10-7)/12+(27-22)/60+13/42=3/12+5/60+13/42=3/12+1/12+13/42=4/12+1
(4*12)-(2*12)
1/2+1/6+1/12+1/20+1/30+1/42+1/56+1/72+1/90=1-1/2+1/2-1/3+1/3-1/4+……1/9-1/10(除了1与1/10,两两抵消)=1-1/10=9/
解题思路:巧算解题过程:varSWOC={};SWOC.tip=false;try{SWOCX2.OpenFile("http://dayi.prcedu.com/include/readq.php?
1/2+1/6+1/12+1/20+1/30+1/42+1/56+1/72=(1-1/2)+(1/2-1/3)+(1/3-1/4)+(1/4-1/5)+(1/5-1/6)+(1/6-1/7)+(1/7
1.11*72+2.22*246+3.33*12=1.11*72+1.11*492+1.11*36=1.11*(72+492+36)=1.11*600=666
3/17*3/4+36/17*0.75-0.75+(12/17)/(4/3)=3/17*3/4+36/17*3/4-3/4+(12/17)*(3/4)=(3/4)[(3+36-17+12)/17]=(
1/4+1/12+1/24+1/40+1/60+1/84+1/112=1/4+1/2(1/6+1/12+1/20+1/30+1/42+1/56)=1/4+1/2(1/2-1/3+1/3-1/4+1/4
求和?1/6=1/2-1/31/12=1/3-1/41/20=1/4-1/51/30=1/5-1/61/42=1/6-1/71/56=1/7-1/8因此上述分数求和=1/2-1/8=3/8
巧算:(100+12.3+23.4)×(12.3+23.4+34.5)-(100+12.3+23.4+34.5)×(12.3+23.4)设:12.3+23.4=A=35.7(A+100)×(A+34.
27*120+73*120=(27+73)*120=100*120=12000
(3-13/13)*12
11+12+13+14+.+29=(11+29)+(12+28)+(13+27)+...+(20+0)=40x9+20=380
12*(13-11)*1
#include#include#includeusingnamespacestd;intb[1100];//数组用来存输入的序列intmain(){stacka;//保存序列的栈stackxb;//
1×2×3+2×3×4+3×4×5+…+10×11×12=(1*2*3*4-0*1*2*3)/4+(2*3*4*5-1*2*3*4)/4+...+(10*11*12*13-9*10*11*12)/4=
答案长度太长,百度不让发,我写在这个帖子里面了:
(12-12÷2)×4
12*(37+43)/24=12*80/24=12*2*40/24=24*40/24=40