Question

二分之一加二分之一乘三分之一加三分之一乘四分之一加四分之一乘五分之一加五

1×1/2+1/2×1/3+1/3×1/4+1/4×1/5+1/5×1/6+1/6×1/7
1×1/2+1/2×1/3+1/3×1/4+1/4×1/5+1/5×1/6+1/6×1/7等于多少
找规律，用简便方法

Answer 1

1×1/2+1/2×1/3+1/3×1/4+1/4×1/5+1/5×1/6+1/6×1/7
=1-1/2+1/2-1/3+1/3-1/4+1/4-1/5+1/5-1/6+1/6-1/7
=1-1/7
=6/7