Question

(1/3)-(1/12)-(1/20)-(1/30)-(1/42) = 等于多少 减去二十分之一减去三十分之一减去四十二

Answer 1

(1/3)-(1/12)-(1/20)-(1/30)-(1/42)

=1/3 -(1/12+1/20+1/30+1/42)

=1/3-(1/3-1/4+1/4-1/5+1/5-1/6+1/6-1/7)

=1/3-(1/3-1/7)

=1/7