Question

(简算)2分之1+6分之5-12分之7+20分之9-30分之11

Answer 1

=(1-1/2) +(1/2+1/3)-(1/3+1/4)+(1/4+1/5)-(1/5+1/6)

=1-1/2+1/2-1/3-1/3-1/4+1/4+1/5-1/5-1/6

=1-1/6

=5/6