幫得幾多得幾多,聽日交，幫我啊！
1.7-x
------ -3=1,x=?
4
2.A sum of money is to be evenly shared among ten person.However,two of them are absent,so each of the 8 attendees gets $30 more.Find the total amount of money.
3.When Alex was born,his mother was 28 years old.His mother is now 3 times as old as Alex.Find his age now.
4.3+6+9+...+300=?
求救！幫我！
F1英數：Algebra，冇乜點數，但求救
2013-10-28 3:15 am
回答 (2)
2013-10-28 3:38 am
✔ 最佳答案
1. 7-x-12=4x=-9
2. x/8=x/10+30
5x=4x+1200
x=1200
3. 3x=28+x
2x=28
x=14
alex is 14 years old
4 3+6+9+...+300
=3(1+2+3+...+100)
=3(1+100)*100/2
=15150
2013-10-28 6:36 am
S = 3 + 6 + 9 + ... + 297+300 .... (1) ... 等號右面共100個數
S = 300+297+....+9+6+3 ............(2) ... 等號右面共100個數
(1)+(2) [ 上下加在一起
2S = 303 + 303 + 303 + 303 + ..... + 303 ... 等號右面共100個數
2S = 100X303
S = (100X303)÷2 = 15150
S = 300+297+....+9+6+3 ............(2) ... 等號右面共100個數
(1)+(2) [ 上下加在一起
2S = 303 + 303 + 303 + 303 + ..... + 303 ... 等號右面共100個數
2S = 100X303
S = (100X303)÷2 = 15150
收錄日期: 2021-04-27 20:34:25
原文連結 [永久失效]:
https://hk.answers.yahoo.com/question/index?qid=20131027000051KK00221