1.
A square floor is covered with carpet, except a border 0.5 m wide, round the carpet, which is covered with linoleum. The carpet and linoleum cost respectively $9 and $5 per m^2. The whole cost is $189. Find the length of the floor.
Ans: 15 m
2.
Divide a line 8 cm long internally into two parts, so that the rectangle contained by the whole line and one part may be twice the square on the other part.
Ans: Each part 4 cm
題目說甚麼?
maths
2007-07-23 7:11 pm
回答 (2)
2007-07-24 9:13 pm
✔ 最佳答案
1.Just like the photo below:http://i207.photobucket.com/albums/bb173/kkkpopup/fig1.jpg
Let x be the length of the floor covered with carpet.(cyan region)
9x^2 + 5[(x + 1)^2 - x^2] = 189
9x^2 + 5(2x + 1) = 189
9x^2 + 10x + 5 = 189
9x^2 + 10x - 184 = 0
(9x + 46)(x - 4) = 0
x=-46/9 (rejected) or x=4
So the length of the floor is 4 + 0.5 + 0.5 = 5m
2. What do you mean by " the rectangle contained by the whole line and one part"?
Please check if you had type it wrong.
2007-07-23 7:45 pm
1. 一個正方形地面鋪著地毯,而它的邊界由0.5米的linoleum圍著。每平方米的地毯要9蚊,linoleum要5蚊。這樣鋪法總共需189蚊。那麼正方形邊長幾多?
設y是有地毯的邊長
9(y^2)+5x((y+0.5+0.5)^2-y^2)=189
9y^2+5x(2y+1)=189
y=4 或-46/9(捨去)
所以: 地毯長4米
因為:地面長=4+0.5+0.5
所以地面長5米
答案應是5米而非15米
設y是有地毯的邊長
9(y^2)+5x((y+0.5+0.5)^2-y^2)=189
9y^2+5x(2y+1)=189
y=4 或-46/9(捨去)
所以: 地毯長4米
因為:地面長=4+0.5+0.5
所以地面長5米
答案應是5米而非15米
收錄日期: 2021-04-13 00:51:45
原文連結 [永久失效]:
https://hk.answers.yahoo.com/question/index?qid=20070723000051KK01072