Question

二分之一加六分之一加十二分之一加二十分之一加三十分之一加四是二分之一等于多少 用简便方法

Answer 1

二分之一加六分之一加十二分之一加二十分之一加三十分之一加四是二分之一
=1/2+1/2-1/3+1/3-1/4+1/4-1/5+1/5-1/6+1/2
=3/2-1/6
=4/3

Answer 2

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

Answer 3

1/2+1/6+1/12+1/20+1/30+1/42
=1/2+3/6-2/6+4/12-3/12+5/20-4/20+6/30-5/30+7/42-6/42
=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

Answer 4

1/2+1/6+1/12+1/20+1/30+1/42
=1/(1×2)+1/(2×3)+1/(3×4)+1/(4×5)+1/(5×6)+1/(6×7)
=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