Question

1/2十5/6一7/12十9/20一11/30十13/42

1/2十5/6一7/12十9/20一11/30十13/42

Answer 1

1/2十5/6一7/12十9/20一11/30十13/42
=1/2 + 5/(2×3)- 7/(3×4)+9/(4×5) - 11/(5×6) +13/(6×7)
=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
=1又1/7

Answer 2

=（6/12+10/12-7/12）+（27/60-22/60）+13/42
=9/12+5/60+13/42
=45/60+5/60+13/42
=50/60+13/42
=5/6+13/42
=35/42+13/42
=48/42
=8/7

Answer 3

1/2+5/6-7/12+9/20-11/30+13/42
=1/2+（1/2+1/3）-（1/3+1/4）+（1/4+1/5）-（1/5+1/6）+（1/6+1/7）
=1/2+1/2+1/7
=1又1/7

Answer 4

8/7