maths! maths! maths!

2009-07-20 1:47 am

p. 19

6. The scale of a map is 1 cm to 200m .
a. Write the scale in the from 1 : x.
b. What is the actual length of a road which measures 15 cm on the map?
c. What is the length of a highway on the map if its actual length is 8 km ?
d. A rectangular football court measures 5 mm x 12 mm on the map. What is its actual area?

7. If five cats can watch five mice in five minutes, how many cats are needed to catch one hundred mice in one hundred minutes?

回答 (1)

老爺子

2009-07-20 3:47 am

✔ 最佳答案

6.
a.
(1 cm) : (200 m)
= (1 cm) : (200 x 100 cm)
= (1 cm) : (20000 cm)
= 1 : 20000

b.
Actual length
= (15 cm) x [(200 m)/(1 cm)]
= 3000 m

c.
Length of the highway on the map
= 8 km
= 8 x 1000 m
= (8000 m) x [(1 cm)/(200 m)]
= 40 cm

d.
Actual area
= {(5/10 cm) x [(200 m)/(1 cm)]} x {(12/10 cm) x [(200 m)/(1 cm)]}
= (100 m) x (240 m)
= 24000 m2

7.
Let n be the number of cats needed.

(5 cats) : (5 mice)/(5 min) = (n cats) : (100 mice)/(100 min)
5 : 1 = n : 1
Hence, n = 5

Ans: 5 cats are needed.

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