## 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.

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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

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2. 1)
The rate at which an athlete runs can help decide the winner of a race.

2)
The speedometer of a car will reflect the speed of a car at any given time in km/h. This shows the rate at which a car is travelling.

3. 1)To calculate the amount of nutrition in certain food.E.g energy bar has 10g of carbohydrates per 100g.
2)When we buy vegetables and poultry,many of them use \$per 100g to calculate the price.

4. 1)To determine the pay a person gets E.g. he is paid \$100 per hour.
2)We can use it to determine how fast a liquid fills something E.g. the water from the hose come out at 20L per second.

5. 1) To find how much petrol must be filled for a fixed amount of money.
2) To find the fastest athlete for world records etc.

6. 1) To find the speed of an object etc the speed of the F1 car was 230km per hour.
2) To determine how fast a job is going to get done etc the servant has 200 more leaves to pluck and she had plucked 20 in a minute, so the job will be done in 10mins.

7. 1) To find out how much one must run to reach the goal on time.
2) to find out how long each interval of a break is to ensure that students have ample time to eat and relax a bit.

8. 1) To find out how fast must you must complete your task to achieve our goal on time.
2) To find out how much water is needed to bake a cake.

9. 1) For the speedometer to gage how fast the car is moving
2)To find out the cost of petrol per litre

10. 1. To find out the Daily salary of a person if he is given \$50 an hour.
2.To find out the average marks a student earned a question in a test.

11. 1) How long a bottle with a capacity of 800ml will take to be filled when water is filling the bottle at a rate of 100ml per second.

2) How long a download would take when its file is 1 gigabyte and the download speed is at a rate of 1 megabytes per second

12. 1) To find out how much time it takes to arrive at the destination

2) To find out how much pace is needed to arrive at the destination

13. 1. How long it would take to make cookies at a factory.