Question

简算：1+三分之一+六分之一+十五分之一+二十一分之一+二十八分之一

Answer 1

1+1/3+1/6+1/15+1/21+1/28
=1+1/(1×3)+1/(2×3)+1/15+1/(3×7)+1/(4×7)
=1+(1/3)(1+1/2)+1/15+(1/7)(1/3+1/4)
=1+(1/3)(3/2)+1/15+(1/7)(7/12)
=1+1/2+1/15+1/12
=(60+30+4+5)/60
=99/60
=33/20