小学奥数计算题简便计算

1、课题复习简便计算教学目标掌握简便运算的方法重 点掌握简便运算的方法难 点掌握简便运算的方法1 1 1 11、 1 22 33 42021 20211111111112、 I _丄_丄_丄_丄十丄+丄+丄2 6122030425672904、1 15 88 111 111 1414 171 195 9898 1015、3334 66 88 10398 1006、18 9 107、丄二十丄 11 匚2481632641282565128、122436485 10 6 12 7 148 12 10 15 12 18 14 214 59、31234 6666543.2 385 3110、1121411

2、2 202014201 1 1 111、1234234534567 8 9 101/(1 X 2X 3X 4)+1/(2 X 3X 4X 5)+1/(3 X 4X 5X 6)+.+1/(7 X 8X 9X 10)=(1/3) X 1/(1 X 2X 3) -1/(2 X 3X 4) +(1/3) X 1/(2 X 3X 4) -1/(3 X 4X 5) +(1/3) X1/(3 X 4X 5) -1/(4 X 5X 6) +.+(1/3) X 1/(7 X 8X 9) -1/(8 X 9X 10):=(1/3) X1/(1 X 2X 3) -1/(2 X 3X 4)+1/(2 X 3X 4)

3、-1/(3 X 4X 5)+1/(3 X 4X 5) -1/(4 X 5X6 )+.+1/(7X 8X 9) -1/(8 X 9X 10):=(1/3) X 1/(1 X2X 3) -1/(8 X 9X 10):=(1/3) X (1/6)-(1/720) =(1/3) X (119/720) =119/21601111 111111111 1 1 12 3 4 53 4 5 62 3 45 63 4 5仅供参考：(1+1/2+1/3+1/4+1/5)*(1/2+1/3+1/+1/5+1/6) - (1+1/2+1/3+1/4+1/5+1/6 ) * (1/2+1/3+1/4+1/5 )设 1

4、+1/2+1/3+1/4+1/5=a1/2+1/3+1/4+1/5=b(1+1/2+1/3+1/4+1/5)*(1/2+1/3+1/4+1/5+1/6)- (1+1/2+1/3+1/4+1/5+1/6 )*( 1/2+1/3+1/4+1/5 )=a*(b+1/6)-(a+1/6)*b=1/6(a-b)=1/613、81.5 15.8 81.5 51.867.6 18.5111111111111111112、8910119101112891011129101114、11Z9些d3 12203042564/3-7/12+9/20-11/30+13/42-15/56=(1+1/3 ) - (1/3+

5、1/4 ) + (1/4-1/5 ) - (1/5+1/6 ) + (1/6+1/7 ) - (1/7+1/8 )=1-1/8=7/815、-4.85 3.6 6.15 3?4 1851 2 3 3 6 9 7 14 2116、1 3 5 3 9 15 7 21 351+3+5+7+9+11+199=(1+199)*100/26135182135 67 X 3 + 6 X 7 + 3 X 72982912299=200*100/2=1000013 5 7 19917、24 6 8 200(1x2x3+3x6x9+7x14x21 (1x3x5+3x9x15+7x21x35) =3(1 X 2+6X 9+7X 14X 7) /3 (1X 5+9X 15+7X 7X 35) =(1 X 2+6X 9+7X 14X 7) /(1 X 5+9X 15+7X 7X 35) =14(4+7X 7)/5(1+3 X 9+7X 7X