f2 . rate and ratio .(3)

herme519

2012-08-09 10:53 pm

(1). The amount of money that Andy.Ben and Cindy have are in the ratio of 3:1:5
If Andy has $600.find the tota; amount of money they have altogether.

(2) In a shop.the ratio of the number of dolls to that of toy cars is 4:3 and the ratio of the number of dolls to that of puzzles is 10:9

(a) Find the number of dolls : the number of toy cars : the number of puzzles.
(b) If the total number of items is212. find the total number of dolls and toy cars.
(c) What is the ratio of the number of toy cars to that of puzzles?

(3) In a map. the perimeter of a rectangular playground is 8cm. The scale of the mao is 1:2000.
(a) Find the actual perimeter of the playground in m.
(b) Suggest one possible area of the playground in the map.
(c) Using the suggested length and width in (b).
(i) find the actual area of the playground.
(ii) find the ratio of the area of the playground in the map to the actual area of the playground.

回答 (1)

andrew

2012-08-09 11:48 pm

✔ 最佳答案

(1)
Let $3k, $k and $5k be the amounts of money that Andy, Ben and Cindy haverespectively.

3k = 600
k = 200

Amount of money they have altogether
= $(3k + k + 5k)
= $9k
= $9 x 200
= $1800

=====
(2)
(a)
Number of dolls : Number of toy cars = 4 : 3 = 20 : 15
Number of dolls : Number of puzzles = 10 : 9 = 20 : 18

Number of dolls : Number of toy cars : Number of puzzles
= 20 : 15 : 18

(b)
Let 20k be the number of dolls.
Then number of the toy cars = 15k
and number of puzzles = 18k

20k + 15k + 18k = 212
53k = 212
k = 4

Total number of dolls and toy cars
= 20(4) + 15(4)
= 140

(c)
Number of toy cars : Number of puzzles
= 15 : 18
= 5 : 6

=====
(3)
(a)
Actual perimeter of the playground
= 8 x 2000 / 100 m
= 160 m

(b)
The playground in the map may be 1 cm x 3 cm.

One possible area of the playground in the map
= 1 x 3 cm²
= 3 cm²
(There are many possible answers.)

(c)(i)
Actual area of the playground
= (1 x 2000 / 100 m) x (3 x 2000 / 100 m)
= 20 x 60 m²
= 1200 m²

(c)(ii)
Area of the playground in the map : Actual area of the playground
= 3 cm² : 1200 m²
= 3 cm² : 1200x(100)² cm²
= 1 : 4000000

參考: andrew

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