數學問題(2)......

2007-11-20 6:03 am
5.今年區議會的總投票人數比上次多20%,而投票的男選民人數比上次多10%,女則多了25%,問今次投票既女選民佔全體人數幾多?
6.If S=15+195+1995+19995+...+199...95(中間有44個9),問S既最後4位數學是多少?
7.現有圓形椅子和方形椅子,每張圓形椅子有3隻腳,每張方形椅子有4隻腳,當佢地全部比人坐上後,共有43隻腳(包括每個人的2隻腳),問有幾多人?
8.A,B2種商品的原價之皈是故150。若A降價10%,B+20%,A+B比原單價之和降了1%,問A+B=幾多?
更新1:

A,B,2種商品的原價之和是150。若A降價10%,B增加20%,A+B興原單價之和降了1%,問A+B=幾多?

回答 (1)

2007-11-20 7:35 am
✔ 最佳答案
5.
Let x be proportion of female voters, then 1-x for male
(1-x) (1.1) + x (1.25) = 1.2
[New M] [New F] [New Population]

Solve x, x= 2/3 #

6.
S= 15+195+1995+19995+.........+199...995
= (15+195+1995) + (20000-5)+(200000-5) + ..........+ (200...00-5)
= 2205 - 42x5 + 20000+200000+................+200..00
[共減了42次5]
= 1995 + 20000+200000+................+200..00
Ans: 1995

7.5x+6y=43
mod 5 operation to check the remainder after divided by 5.
5x mod 5 = 0
6y mod 5= y mod 5 (As 6 mod 5 = 1)
43 mod 5 = 3 mod 5
y=3 ( -2, 8 and the others are impossible)
x=5
x+y=8 #

8.
太多錯別字
參考: me


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