Question

二分之一减六分之一减十二分之一减二十分之一……减九十分之一等于几

Answer 1

1/2-1/6-1/12.1/90
=1/2-(1/2-1/3)-(1/3-1/4)-.(1/9-1/10)
=1/2-1/2+1/3-1/3+1/4-.-1/9+1/10
=1/10