1 2+4+6+......+74+76+78=?
2 15+17+19+.....+33+35+37=?
3 26+27+28+.....+46+47+48=?
多謝!
數學問題!
2007-01-26 10:53 pm
回答 (7)
2007-01-27 9:26 pm
1) 2+4+6+......+74+76+78
=2(1+2+3+4+5+6......+37+38+39)
=2[(1+39)(39/2)]
=2(40)(19.5)
=2(780)
=1560
2) 15+17+19+.....+33+35+37
=(15+37)[(37-15)/2+1]/2
=52(22/2+1)/2
=52(12)/2
=52(6)
=312
=2(1+2+3+4+5+6......+37+38+39)
=2[(1+39)(39/2)]
=2(40)(19.5)
=2(780)
=1560
2) 15+17+19+.....+33+35+37
=(15+37)[(37-15)/2+1]/2
=52(22/2+1)/2
=52(12)/2
=52(6)
=312
2007-01-27 8:06 pm
1.1560
2.312
3.774
I hope can help you.
2.312
3.774
I hope can help you.
2007-01-27 3:22 am
1) 2+4+6+......+74+76+78
=(2+78)×[(78-2)÷2+1]
=80×39
=3120
2) 15+17+19+.....+33+35+37=?
=(15+37)×[(37-15)÷2+1]
=52×12
=624
3) 26+27+28+.....+46+47+48
=(26+48)×(48-26+1)
=74×23
=1702
=(2+78)×[(78-2)÷2+1]
=80×39
=3120
2) 15+17+19+.....+33+35+37=?
=(15+37)×[(37-15)÷2+1]
=52×12
=624
3) 26+27+28+.....+46+47+48
=(26+48)×(48-26+1)
=74×23
=1702
2007-01-27 12:30 am
1 1400
2 312
3 851
2 312
3 851
2007-01-26 11:55 pm
解 :
1.1560
2.312
3.774
1.1560
2.312
3.774
2007-01-26 11:32 pm
1.(2+78)[(78-2)/2+1]/2
=80*39/2
=40*39
=1560
2.(15+37)[(37-15)/2+1]/2
=52*7/2
=26*7
=182
3.(26+48)[(48-26)/1+1]/2
=74*23/2
=37*23
=774
=80*39/2
=40*39
=1560
2.(15+37)[(37-15)/2+1]/2
=52*7/2
=26*7
=182
3.(26+48)[(48-26)/1+1]/2
=74*23/2
=37*23
=774
收錄日期: 2021-04-12 22:51:05
原文連結 [永久失效]:
https://hk.answers.yahoo.com/question/index?qid=20070126000051KK01499