六年级数奥题一堆.【1】1-1/2-1/4-1/8-1/16-1/32-1/64【2】1/2002＋2/2002＋3/2
5个回答
【1】1-1/2-1/4-1/8-1/16-1/32-1/64
=1-1/2-1/4-1/8-1/16-1/32-1/64-1/64+1/64
=1-1/2-1/4-1/8-1/16-1/32-1/32+1/64
=1-1/2-1/4-1/8-1/16-1/16+1/64
=1-1/2-1/4-1/8-1/8+1/64
=1-1/2-1/4-1/4+1/64
=1-1/2-1/2+1/64
=1-1+1/64
=1/64
【2】1/2002＋2/2002＋3/2002＋4/2002-5/2002-6/2002-7/2002-8/2002＋9/2002.＋2001/2002＋2002/2002
=[(1＋2＋3＋4-5-6-7-8)＋(9+.)＋2001＋2002]/2002 8个数一组,共250组零两个
=[(-16)*250＋2001＋2002]/2002
=[-4000＋2001＋2002]/2002
=3/2002
【3】1/2＋(1/3＋2/3)＋(1/4＋2/4＋3/4)＋(1/5＋2/5＋3/5＋4/5)＋.＋(1/20＋2/20＋3/20＋.＋18/20＋19/20)
=1/2+2/2+3/2+4/2+.+19/2
=(1+2+3+4+.+19)/2
=[19*(19+1)/2]/2
=19*20/4
=19*5
=95
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