Wednesday, June 8, 2011

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


  1. 1)The price of oil per gallon in Los Angeles is $3.93/gallon.

    2)The average wind speed of a level 1 hurricane is 37.5 m/s.



  2. 1. The speed limit for an expressway in Singapore is about 80km/h.

    2. The price of fabric in Malaysia is about RM 5/m

  3. 1)The speed of light is 299,792,458m/s
    2)The fastest speed of the F1 car is 360KM/h

  4. 1) The charge for electricity in Singapore is $0.2558/kW
    2) The charge for water in Singapore is $1.1700/Cu M

  5. 1) The heartbeat of an average men is 64 - 72 beats per minute while the heartbeat of average women is 72 - 80 beats per minute.

    2) The speed of hair growth is roughly 1.25 centimeters or 0.5 inches per month, being about 15 centimeters or 6 inches per year. With age, the speed of hairgrowth might slow down to as little as 0.25 cm or 0.1 inch a month.

  6. Dylan Goh Kai Xiang6/28/2011 07:04:00 AM

    1) The speed of a bullet is about 400m/s
    2) The speed of sound is about 344.4 meters per second.

  7. 1) The price of the patrol in Australia is 1.493/l
    2) The speed limit in the highways are usually 100km/h.

  8. 1) the amount paid for electricity in Singapore is $0.2558/kW

    2)the speed of formula one race car is about 330km/h 205mph

  9. The speed of light is299,792,457 m/s
    The speed of F1 cars are usually 330 km/h

  10. 1) The speed of Sound it 340.29 m/s
    2)A tsunami travels at 600 m/h


  11. 1.A tornado moves at an average speed of about 30 miles per hour
    2.The price for electricity in Singapore is $0.2558/kW

  12. 1) The speed of F1 cars are about 330 km/h
    2) The normal heart rate for adults aged 18-55 years old is 60-100 beats per minute

  13. 1. 1.8 people die each second.
    2. 3 babies are born each second.

  14. 1. The speed of the MRT train is about 70km/h above the tunnel. In the tunnel, the speed is faster which is about 90km/h.
    2. The average speed of road bikes is 18 to 22m/h.