Question

20-3分之2-15分之2-35分之2-63分之2-99分之2 简便

Answer 1

2/3=1-1/3
2/15=1/3-1/5
2/35=1/5-1/7
...
所以原式=20-1+1/3-1/3+1/5-1/5...-1/9+1/11
=20-1+1/11
=19又1/11