Question

简算）1-5/6+7/12-9/20+11/30-13/42+15/56-17/72+19/90-21/110

Answer 1

1-(2+3)/2*3+(3+4)/3*4-(4+5)/4*5+..........-(10+11)/(11*10)
=1-1/2-1/3+1/3+1/4-1/4-1/5+........-1/10-1/11
=1-1/2-1/11
=1/2-1/11
=9/22

Answer 2

1-（1/2+1/3)+(1/3+1/4)-……