1.)The length of a rectangular field(長方形草地)is three times as long as its width. If the width is increased by 10m
and its length remains unchanged, the area of the field will be increased by 900 m(2次方)
(a.)Find the original length and width of the field.
(b.)Find the new area of the field.
(c.)What is the new perimeter of the field?
2.The marked price of a watch is $(3y+10). Mr.Chan buys it at a discount of 20% and he pays $(2y-40) less than the marked price.
a.Find the value of y.
b.What is the maeked price?
c.How much does Mr Chan pay for the watch?
以有要式同步驟就得..急..要方程..英文..thx~15點
F.1 ENG math ..15 points
2008-11-08 1:26 am
回答 (2)
2008-11-08 2:01 am
✔ 最佳答案
1, Let X be the width of the field.a, 3X(10m+X)-3X^2=900m^2
30X+3X^2-3X^2=900m^2
30X=900m^2
X=30m
Width = 30m
Length = 90m
b, New area = 40*90 = 3600m^2
c, 40*2+90*2=260m
2, (3y+10)*(20%)=2y-40
a, 0.6y+2=2y-40
1.4y=42
y=30
b,marked price = 3*30+10 = 100
c, 100- (2*30-40) = 80
2008-11-08 1:46 am
1)
a)
Let the original length be Y m so width be 3Y m.
(3y + 10) * y - 900 = 3y * y
3y^2 + 10y - 900 = 3y^2
10y - 900 = 0
y = 90
So , the original length and width is 90 m and 270 m
b)
The new area is (3y + 10) * y = 3y^2 + 10y
Put y = 90 ,
3 * 90 * 90 + 10 * 90
= 270 * 90 + 10 * 90
= 280 * 90
= 25200 m^2
c)
The new perimeter = 90 * 2 + 270 * 2 = 360 * 2 = 720 m
2)
a)
(3y + 10) * (1 - 20%) = (3y + 10) - (2y - 40)
(3y + 10) * 4 / 5 = y + 50
12y + 40 = 5y + 250
7y = 210
y = 30
b)
The marked prize = $(3y + 10) = $100
c)
He paid :
100 * (1 - 20%)
= 100 * 80%
= $80
a)
Let the original length be Y m so width be 3Y m.
(3y + 10) * y - 900 = 3y * y
3y^2 + 10y - 900 = 3y^2
10y - 900 = 0
y = 90
So , the original length and width is 90 m and 270 m
b)
The new area is (3y + 10) * y = 3y^2 + 10y
Put y = 90 ,
3 * 90 * 90 + 10 * 90
= 270 * 90 + 10 * 90
= 280 * 90
= 25200 m^2
c)
The new perimeter = 90 * 2 + 270 * 2 = 360 * 2 = 720 m
2)
a)
(3y + 10) * (1 - 20%) = (3y + 10) - (2y - 40)
(3y + 10) * 4 / 5 = y + 50
12y + 40 = 5y + 250
7y = 210
y = 30
b)
The marked prize = $(3y + 10) = $100
c)
He paid :
100 * (1 - 20%)
= 100 * 80%
= $80
收錄日期: 2021-05-01 16:17:40
原文連結 [永久失效]:
https://hk.answers.yahoo.com/question/index?qid=20081107000051KK01054