### June Vacation Chap 9.2 RATE (L1) Rate in Everyday Situation

What's defined in Wikipedia: Rate (mathematics)
In mathematics, a rate is a ratio between two measurements, often with different units.[1]. If the unit or quantity in respect of which something is changing is not specified, usually the rate is per unit time. However, a rate of change can be specified per unit time, or per unit of length or mass or another quantity. The most common type of rate is "per unit time", such as speed, heart rate and flux. Rates that have a non-time denominator include exchange rates, literacy rates and electric flux.

When we describe the units of a rate, the word "per" is used to separate the units of the two measurements used to calculate the rate (for example a heart rate is expressed "beats per minute"). A rate defined using two numbers of the same units (such as tax rates) or counts (such as literacy rate) will result in a dimensionless quantity, which can be expressed as a percentage (for example, the global literacy rate in 1998 was 80%) or fraction or as a multiple.

~~~~~~~~~~~~~~~~~~~~~
Rate is commonly used in our daily life. Here are some examples:

40 km/h - 40 kilometres per hour
30 steps/min - 30 steps in per minute
2 l/hour - 2 litres per hour
67 words/min - 60 words per 1 min
80 m/week - 80 metres per week
25km/l - 25 kilometres per 1 litre
\$90/m³ - \$90 per cubic metre

Think of 2 real life situations in which we use the concept of rate to describe useful information.

Here is an example:
The Singapore Flyer rotates at the rate of 0.24 m/s or 0.76 km/h

3. @Christabel: thanks :D

4. the speed of light = 299 792 458 m / s

5. 1. When showering, water flows out at a constant rate. Normally, water flows at a rate of 2.2 gallons of water per minute which is 8.33 liters of water per minute.

An average walking rate is 15 minutes per mile so in one hour the average rate is 4 miles per hour.

6. I tweet at 50tweets/hr

7. speed of sound is 340.29 m / s

8. Terrorist kill people at 10 thousand people a year in the whole world.
People abuse dogs at 100,000 dogs a year.

9. I can type 10 letters in 1s [Rate 10 letters/s]

I can say 20 words in 10s [Rate 20 words/s]

10. i eat 10 burgers/ hour

11. 1: the car goes by 11km/liter

12. 1.41346 usd/euro
http://www.xe.com/ucc/

13. Average speed of a driver on a highway in Singapore is 80km/h

14. 1) The speed of light is 299 792 458 m / s
2) The speed of sound is 340.29 m / s

15. The fan spins at 130 rounds per minute.
We are now typing 3 letters per second.

17. 100 thousand people are enter mental hospital a year.
People (Matthew) fart 100 times a minute :D

AK 47 fires at a rate of 60 rounds/minute

19. 1.04482 usd/aud
http://www.xe.com/ucc/

20. the speed of snails is 0.013 m/s

21. Music Bank shows 2 host/show :DD
Music Core shows 4 host/show :DD
M! Countdown shows 3 host/show :DD
Inkigayo shows 4 host/show :DD

22. Hubble Space Telescope orbits at 17500 mph (28000 kph)

23. Miss Loh is giving us pop quiz at a rate of 2 pop quiz/1 month(4 weeks)

24. Average walking speed is 1km/h
The washing machine washes 30pieces of clothing in a 1h

26. 1)I read 10 pages of my book in 20 minutes (1/2 page/min)

2)I run 2.4km in 12 minutes (1/5km/min)

27. John can type at the rate of 5letter/sec