计算(1).5+10+15+20+25+...+85+90+95+100(2).(1+3+5+7+...+1991)-(

3个回答

  • 1)

    项数=(末项-首项)/ 公差 + 1 = (100 - 5 )/ 5 + 1 = 20

    求和=(首项+末项)*项数 / 2 = ( 5+100)* 20 / 2 = 1050

    2)

    =1+(3-2)+(5-4)+.+(1991-1990) = 1+ 1+1+.+ 1 = 996

    3)

    5 - (5*5 -5)/5 = 1

    4)

    (5+5)/5+5-5=2

    5)

    (5*5-5-5)/5=3

    6)

    125*27+54*125-125= 125*(27+54-1) = 125 * 80 = 10000

    7)

    (104*112*198)/(224*52*198)= (2*52*112*198) / (112*2*52*198) =1

    8)

    117684 / 12 = 9807