(9999+9997+···+9001)—(1+3+5+····+999)=?
问题描述:
(9999+9997+···+9001)—(1+3+5+····+999)=?
答
=999*9000
=8991000
答
原式=9001-1+9003-3+9005-5+……+9999-999=9000*500=4500000
答
(9999+9997+···+9001)—(1+3+5+····+999)
=(9999+9901)×50/2-(1+999)×500/2
=497500-250000
=247500