maths! maths! maths!

2009-07-24 5:19 am

p. 17
1. If a : b = c : d, which of the following is ture?
a. ab=cd b. ac=bd c. ad=bc d. a+c=b+d
2. The scale of a map is 1 : 100000. If a road is measured to be 5 cm on the map, what is the actual length of the road?
a. 500m b. 5km c. 50km d. 500km
3. The scale of a map is 1:5000. If a park is measured to be 4cm x 3cm on the map, what is its actual area?
a. 3000m2 b. 30000m2 c. 60000m2 d. 300000m2
4. If a:b = 3:2 and b:c = 3:4, find a:b:c.
a. 3:2:4 b. 6:4: 3 c . 9:6:8 d. 9:8:6
5. If (2x-y) : (2x+y) = 3:7, then x:y =
a. 2:1 b. 4: 5 c .5:4 d. 7:3

6. If a:c = 1:2 and b:a = 2:3, find a:b:c.

紅色的是上標字.

回答 (1)

cipker

2009-07-24 5:31 am

✔ 最佳答案

1. If a : b = c : d

a/b= c/d

ad=bc

Ans :(c)

2.

1 : 100000 = 5 cm : Actual length

Actual length/5 cm = 100000
Actual length = 500000 cm = 500m

Ans (a)

3.
Area of park in map = 4cm x 3cm = 12cm^2 = 0.0012 m^2

1^2 :5000^2 = 0.0012 m^2 : Actual area
Actual area/ 0.0012 m^2 = 5000^2
Actual area = 30000 m^2

Ans (b)

4
a:b = 3:2 = 9 :6
b:c = 3:4 = 6:8
a:b:c = 9 : 6 :8

Ans (c)

5.
(2x-y) : (2x+y) = 3:7,
(2x-y)/(2x+y)=3/7
7(2x-y)=3(2x+y)
14x - 7y = 6x + 3y
8x = 10y
x/y = 10/8= 5/4
x : y =5:4

Ans (c)

6.

a:c = 1:2 = 3:6
a:b = 3:2

a:b:c = 3 : 2 : 6

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