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RATES
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RaTEs A rate is a ratio that compares quantities measured in different units. For example, the speed of a car is measured in km/h (kilometres per hour). The ‘per’ symbol (/) is also a form of division. Rates may be calculated by dividing the two quantities measured.
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Example #1: What is the average speed of a car that travelled 360km in 4 hours? Average speed (km/h) = 360km / 4h = 360 divided by 4 = 90km/h
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Example #2: What is the run rate of a one-day cricket team that scored 300 runs in 50 overs? Run rate (runs/over) = 300 runs / 50 overs = 300 divided by 50 = 6 runs/over
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HOMEWORK: Complete proportion worksheet
In your Math journal, complete all questions on pg 82/83. Show your working out.
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Converting Units of Measurement:
Some rate problems will involve different units of measurement. Remember, when solving rate problems all RATIOS must be in PROPORTION (equal measurements).
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COMMON UNITS: mm-cm-m-km 10mm=1cm 100cm=1m 1000m=1km ml-L 1000ml=1L g-kg 1000g=1kg sec-mins-hours 60secs=1 minute 3600secs=1 hour
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PRACTICE PROBLEMS: Solve these problems involving rates:
What is the average speed of a train that travelled 600km in 3 hours? What is the cost per minute of an 8 minutes phone call costing $2.40? Mr James ran 26 kilometres in 2 and a half hours. How fast did he run per hour? How fast did he run per minute? 2. Solve these problems involving rates: What is the cost per metre of 7m of rope that costs $21? A driver takes 10 hours to travel from Sydney to Melbourne. What is the average speed for this 880km trip? The UAE needs 81 runs in the next 9 overs to win a one-day cricket match. What run rate is required? The 1400km plane ride from Sharjah to Egypt takes 3 hours. What is the average speed of the aircraft? A patient’s heart beats 360 times in 5 minutes. What is the patient’s heart rate in beats per minute? A 20 litre can of paint costs $80. What is the cost per litre? A taxi driver paid $90 for 60L of fuel. What is the cost per litre?
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