1/1*4+1/4*7+1/7*10+1/10*13+~+1/97*100

=(1/3)*[(1-1/4)+(1/4-1/7)+(1/7-1/10)+...+(1/97-1/100)]
=1/3[1-1/4+1/4-1/7+.......1/97-1/100]
=(1/3)*(1-1/100)
==33/100

1/1*4+1/4*7+1/7*10+1/10*13+~~~+1/97*100
=(1/3)*[(1-1/4)+(1/4-1/7)+(1/7-1/10)+...+(1/97-1/100)]
=(1/3)*(10-1/4+1/4-1/7+1/7-1/10+1/10+...+1/97-1/100)
=(1/3)*(1-1/100)
=(1/3)*(99/100)
=33/100

1/1*4+1/4*7+1/7*10+1/10*13+~+1/97*100
=(1/3)*[(1-1/4)+(1/4-1/7)+(1/7-1/10)+...+(1/97-1/100)]
=(1/3)*(1-1/100)
=(1/3)*(99/100)
=33/100

1/1*4+1/4*7+1/7*10+1/10*13+.........+1/2002*2005
=[1-1/4+1/4-1/7+1/7-1/10+1/10-1/13+.....+1/2002-1/2005]/3
=[1-1/2005]/3
=2004/(2005*3)
=668/2005
貌似和这个题一样