1*2/1+2*3/1+3*4/1+4*5/1+5*6/1+6*7/1+7*8/1+8*9/1+9*10/1等于多少?用简便方法

问题描述:

1*2/1+2*3/1+3*4/1+4*5/1+5*6/1+6*7/1+7*8/1+8*9/1+9*10/1等于多少?用简便方法

1/1*2+1/2*3+1/3*4+1/4*5+1/5*6+1/6*7+1/7*8+1/8*9+1/9*10
=1-1/2+1/2-1/3+1/3-1/4+1/4-1/5+1/5-1/6+1/6-1/7+1/7-1/8+1/8-1/9+1/9-1/10
=1-1/10
=9/10