Question

30分之1+42分之1+56分之1+72分之1+.2450分之1

Answer 1

1/30+1/42+1/56+.1/2450

=1/(5*6)+1/(6*7)+1/(7*8)+.+1/(49*50)

=1/5-1/6+1/6-1/7+1/7-1/8+.+1/49-1/50

=1/5-1/50

=9/50