五年级成绩的简单计算

1、

(90+1/88)×1/89

=(90×88+1)/88×1/89

=[(89+1)×(89-1)+1]/88×1/89

=[89^2-1^2+1]/88×1/89

=89^2/88×1/89

=89/88

2、

(1/3-1/4)+(1/4-1/5)+(1/5-1/6)

=1/3-1/4+1/4-1/5+1/5-1/6

=1/3-1/6

=1/6

3、

1-1/(1*2)+1/(2*3)+……+1/50*51

=1-(1-1/2)+(1/2-1/3)+……+(1/50-1/51)

=1-1+1/2+1/2-1/3+1/3-1/4……+1/50-1/51

=1-1/51

=50/51

没有计算过程:

1.(1/2+1/4+1/6+1/8)-(1/3+1/6+1/9+1/12)+(1/4+1/8+1/12+1/ 16)-(1/5+1/10+1/15+1/20)

2.(260/31÷374/161÷598/197)/42÷(1/2+1/3+1/5)

3.(1/2+1/3+1/5)÷1/30+(1/3+1/5+1/7)÷1/105+(1/5+1/7+1/9)÷1/315

4.(1/11+1/21+1/31+1/41)×(1/21+1/31+1/41+1/ 51)-(1/11+1/21+1/31+1/41+1/51)×(1/21+1/31+1/41)

5.(1+1/2+1/3+……+1/1999)×(1/2+1/3+……+1/2000)-(1+1/2+1/3+……1/2000)×(1/2+1/3+……+1/1999)

6.(1-1/2^2)×(1-1/3^2)×(1-1/4^2)×……×(1-1/2008^2)