Starter quiz
- An ______ rate is the rate at which one currency is exchanged for another. The two currencies are in proportion because they have a constant multiplicative relationship.
- 'exchange' ✓
- For every 1 nugget you get 3 chips. Use this statement to decide which of the following are true?
- 2 nuggets and 4 chips
- 2 nuggets and 6 chips ✓
- 5 nuggets and 7 chips
- 5 nuggets and 15 chips ✓
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- The ratio of A : B is 1 : 6. What is the multiplicative relationship between A and B?
- B = A
- B = A + 5
- B = A × 6 ✓
- A = B 5
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- The ratio of A : B is 2 : 3. What is the multiplicative relationship between A and B?
- B = A + 1
- B = A × 1.5 ✓
- A = B 1
- B = A
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Does this graph show direct proportion?- Yes ✓
- No
-
What is the missing value in this ratio table?- '25' ✓
Exit quiz
- What does 'mpg' stand for?
- 'miles per gallon' ✓
- Which of these ratios represents this sentence? For every 1 dollar you get 56 pence
- $1 : 56
- 56 p : $1 ✓
- $1 : £0.56 ✓
- £1 : $0.56
- $1 : £56
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- Izzy says, "I changed £200 and got $254". What is this as a unit ratio in pounds?
- £200 : $254
- £100 : $127
- £1 : $1.27 ✓
- £0.79 : $1
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- Andeep says, "I changed £300 and got €400". What is this as a unit ratio in euros?
- £1 : €1.33
- £300 : €400
- €100 : £75
- £0.75 : €1 ✓
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- A tap fills at a rate of 16 litres per minute. How long will it take to fill a paddling pool with a capacity of 400 litres?
- '25 minutes' ✓
Calculate the cost of electricity. Give your answer to the nearest penny.- '£203.87' ✓
Worksheet
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Lesson Details
Key learning points
- Direct proportion can be used in a number of contexts, for example in currency conversion.
- Proportional relationships can be expressed as ratios, often in unitary form.
- A ratio is in unitary form if one of the parts is equal to one.
- It is useful to be able to recognise which contexts involve direct proportion.
Common misconception
When considering meter readings, using the 'new reading' rather than the units used to calculate the cost.
Emphasise that it is the change in readings that indicates the units used during a time period. The 'new reading' alone shows the total number of units used since the meter was installed.
Keywords
Rate - A rate is a relationship between two units. For example miles per hour (mph) is a rate called speed which relates distance and time.
Exchange rate - An exchange rate is the rate at which one currency is exchanged for another. The two currencies are in proportion because they have a constant multiplicative relationship.
Direct proportion - Two variables are in direct proportion if they have a constant multiplicative relationship.
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