Question

0.1+0.3+0.5+0.7+0.9+1.1···19.7+19.9 求脱式计算。

Answer 1

0.1+0.3+0.5+0.7+0.9+1.1···19.7+19.9=0.4+0.5+0.7+0.9+1.1···19.7+19.9=0.9+0.7+0.9+1.1···19.7+19.9=1.6+0.9+1.1···19.7+19.9=2.5+1.1···19.7+19.9=3.6+1.3···19.7+19.9=4.9+1.5···19.7+19.9=6.4+1.7···19.7+19.9=8.1+1.9···19.7+19.9=10+2.1···19.7+19.9=12.1+2.3···19.7+19.9=14.4+2.5···19.7+19.9=16.9+2.7···19.7+19.9=19.6+2.9···19.7+19.9=22.5+3.1···19.7+19.9=25.6+3.3+···19.7+19.9=28.9+3.5+···19.7+19.9=32.4+3.7+···19.7+19.9=36.1+3.9+···19.7+19.9=40+4.1+···19.7+19.9=44.1+4.3+···19.7+19.9=48.4+4.5+···19.7+19.9=52.9+4.7+···19.7+19.9=57.6+4.9+···19.7+19.9=62.5+5.1+···19.7+19.9=67.6+5.3+···19.7+19.9=72.9+5.5+···19.7+19.9=78.4+5.7+···19.7+19.9=84.1+5.9+···19.7+19.9=90+6.1+···19.7+19.9=96.1+6.3+···19.7+19.9=102.4+6.5+···19.7+19.9=108.9+6.7+···19.7+19.9=115.6+6.9+···19.7+19.9=122.5+7.1+···19.7+19.9=129.6+7.3+···19.7+19.9=136.9+7.5+···19.7+19.9=144.4+7.7+···19.7+19.9=152.1+7.9+···19.7+19.9=160+8.1+···19.7+19.9=168.1+8.3+···19.7+19.9=176.4+8.5+···19.7+19.9=184.9+8.7+···19.7+19.9=193.6+8.9+···19.7+19.9=202.5+9.1+···19.7+19.9=211.6+9.3+···19.7+19.9=220.9+9.5+···19.7+19.9=230.4+9.7+···19.7+19.9=240.1+9.9+···19.7+19.9=250+10.1+···19.7+19.9=260.1+10.3+···19.7+19.9=270.4+10.5+···19.7+19.9=280.9+10.7+···19.7+19.9=291.6+10.9+··19.7+19.9=302.5+11.1+···19.7+19.9=313.6+11.3+···19.7+19.9=324.9+11.5+···19.7+19.9=336.4+11.7+···19.7+19.9=348.1+11.9+···19.7+19.9=360+12.1+···19.7+19.9=372.1+12.3+···19.7+19.9=384.4+12.5+···19.7+19.9=396.9+12.7+···19.7+19.9=409.6+12.9+···19.7+19.9=422.5+13.1+···19.7+19.9=435.6+13.3+···19.7+19.9=448.9+13.5+···19.7+19.9=462.4+13.7+···19.7+19.9=476.1+13.9+···19.7+19.9=490+14.1+···19.7+19.9=504.1+14.3+···19.7+19.9=518.4+14.5+···19.7+19.9=532.9+14.7+···19.7+19.9=547.6+14.9+···19.7+19.9=562.5+15.1+···19.7+19.9=577.6+15.3+···19.7+19.9=592.9+15.5+···19.7+19.9=608.4+15.7+···19.7+19.9=624.1+15.9+···19.7+19.9=640+16.1+···19.7+19.9=656.1+16.3+···19.7+19.9=672.4+16.5+···19.7+19.9=688.9+16.7+···19.7+19.9=705.6+16.9+···19.7+19.9=722.5+17.1+···19.7+19.9=739.6+17.3+···19.7+19.9=756.9+17.5+···19.7+19.9=774.4+17.7+···19.7+19.9=792.1+17.9+···19.7+19.9=810+18.1+···19.7+19.9=828.1+18.3+···19.7+19.9=846.4+18.5+···19.7+19.9=864.9+18.7+···19.7+19.9=883.6+18.9+···19.7+19.9=902.5+19.1+···19.7+19.9=921.6+19.3+19.5+19.7+19.9=940.9+19.5+19.7+19.9=960.4+19.7+19.9=981.1+19.9=1000

Answer 2

用等差数列求和：（首项+末项）*项数/2
项数：（末项-首项）/公差+1
所以，原式=(0.1+19.9)[(19.9-0.1）/0.2+1]/2
=1000

Answer 3

（19.9-0.1）÷0.2+1=100
0.1+0.3+0.5+0.7+0.9+1.1···19.7+19.9
=（0.1+19.9）X100÷2
=1000

Answer 4

解：原式=（0.1+19.9）*100*1/2
=20*50
=1000

Answer 5

奥数吗，（技巧）0.1+19.9+0.3+19.7+0.5+19.5+0.7+19.3+1+19 就这样算。。。。
=20+（50个 20）慢慢写
=1000