數學題:【簡便運算】: 記住要詳細d, 寫埋條式!!
1) 123+234+345+456+567+678+789
2) 1212-1111+1010-909+808-707+606
3) 999-99-1899+2001
數學題: 記住: 【簡便運算】
2007-02-04 4:43 am
回答 (3)
2007-02-04 4:57 am
✔ 最佳答案
1) 123+234+345+456+567+ 678+789= 100 + 220 + 333 + 444 + 555 + 666 + 777 + 88 + 9
=320 + 2775 + 97
=3095 + 97
= 3192
2) 1212-1111+1010-909+8 08-707+606
=(1212-1111)+(1010-909)+(8 08-707)+606
=101 + 101 + 101 + 606
=909
3) 999-99-1899+2001
=(1000 - 1) - (100 - 1) - (1900 - 1) + 2000 + 1
= 1000 - 100 - 1900 + 2000 - 1 + 1 + 1 + 1
= 1000 - (100 + 1900 - 2000) -(1-1) + 2
= 1000 + 2
= 1002
2007-02-04 6:56 pm
1) 123+234+345+456+567+ 678+789
= 100 + 220 + 333 + 444 + 555 + 666 + 777 + 88 + 9
=320 + 2775 + 97
=3095 + 97
= 3192
2) 1212-1111+1010-909+8 08-707+606
=(1212-1111)+(1010-909)+(8 08-707)+606
=101 + 101 + 101 + 606
=909
3) 999-99-1899+2001
=(1000 - 1) - (100 - 1) - (1900 - 1) + 2000 + 1
= 1000 - 100 - 1900 + 2000 - 1 + 1 + 1 + 1
= 1000 - (100 + 1900 - 2000) -(1-1) + 2
= 1000 + 2
= 1002
= 100 + 220 + 333 + 444 + 555 + 666 + 777 + 88 + 9
=320 + 2775 + 97
=3095 + 97
= 3192
2) 1212-1111+1010-909+8 08-707+606
=(1212-1111)+(1010-909)+(8 08-707)+606
=101 + 101 + 101 + 606
=909
3) 999-99-1899+2001
=(1000 - 1) - (100 - 1) - (1900 - 1) + 2000 + 1
= 1000 - 100 - 1900 + 2000 - 1 + 1 + 1 + 1
= 1000 - (100 + 1900 - 2000) -(1-1) + 2
= 1000 + 2
= 1002
2007-02-04 5:11 am
1) (123+789)+(234+678)+(345+567)+456
=912+912+912+456
=1000+1000+1000+212
=3212
2)101+101+101+606
=303+606
=909
3)(999-99)+2001-1899
=2001+900-1899
=2900-1899+1
=1001+1
=1002
=912+912+912+456
=1000+1000+1000+212
=3212
2)101+101+101+606
=303+606
=909
3)(999-99)+2001-1899
=2001+900-1899
=2900-1899+1
=1001+1
=1002
參考: 自己
收錄日期: 2021-04-23 19:37:40
原文連結 [永久失效]:
https://hk.answers.yahoo.com/question/index?qid=20070203000051KK04084