F.2 maths(SO easy)

1)
Yvonne types 36 words in 40seconds

Her typing rate in words/min

= 36 / (40 / 60) words/min

= 36 * 60 / 40 words/min

= 54 wors/min

2)
0.25kg of fish cost $25

0.25 * 1000g of the fish cost $25

250g of the fish cost $25

The rate in $/100g

= 25 * 100 / (0.25 * 1000) $/100g

= $10 / 100g

3)
1920 vehicles in 2hours

the rate in vehicles/min

= 1920 / (2 * 60) vehicles/min

= 16 vehicles/min

2010-09-06 19:18:43 補充：
2)
0.25kg of fish cost $28

0.25 * 1000g of the fish cost $28

250g of the fish cost $28

The rate in $/100g

= 28 * 100 / (0.25 * 1000) $/100g

= $11.2/100g

Yvonne types 36 words in 40 seconds.[words/min]

Average speed of typing = 36 words/40 second = 0.9 words per second
In 60 seconds Yvonne can type = 0.9 words per second x 60 s = 54 words
1 minute = 60 seconds
Yvonne types 54 words /min.


0.25 kg of fish costs $28 [$/100g]

0.25 kg = 0.25 x 1000 g = 250 g [1 kg is 1000 g]
250 g of fish costs $28.00
1 g of fish costs = $28.00/250g = $0.112
100 g of fish costs = $0.112/g x 100g =$11.20
The fish costs $11.20 per 100 g
 
As for the final answer, money is always expressed in 2 decimal places if the unit is in dollar and it involves cents.


1920 vehicles arrived at a traffic junction between 7am and 9an yesterday.[vehicles/min]

Between 7:00 am and 9:00 am, there are 2 hours ( 9-7 = 2 h)
2 hours = 2 x 60 min. = 120 min. (1 h = 60 min.)
1920 vehicles arrived in 120 min.
Number of vehicles per min. = 1920 vehicles/120 min. = 16 vehicles/min.
 
16 vehicles/min arrived at a traffic junction between 7 am and 9 am yesterday.