Direct proportion graphs
The Maths Habit Handout to print
Taxi A charges £2 a mile.
Taxi B charges £5 to start,
then £1.50 a mile.
Which taxi would you choose?
Taxi A for trips under 10 miles
Taxi B for trips over 10 miles
At 10 miles both cost £20
- Origin
- The point (0, 0), where the axes cross.
The cost of hiring a bike is directly proportional to the number of hours. 2 hours costs £12.
| Hours | 1 | 2 | 3 | 4 |
|---|---|---|---|---|
| Cost (£) | 12 |
A straight line through (0, 0)
5 litres of paint cost £20.
Draw the graph. Find the cost of 3 litres.
| Litres | 1 | 2 | 3 | 4 | 5 |
|---|---|---|---|---|---|
| Cost (£) | 4 | 8 | 12 | 16 | 20 |
4 kg of sand costs £6.
Draw the graph. Find the cost of 3 kg.
| kg | 1 | 2 | 3 | 4 |
|---|---|---|---|---|
| Cost (£) | 1.50 | 3 | 4.50 | 6 |
5 litres of paint cost £20.
Draw the graph. Find the cost of 3 litres.
| Litres | 1 | 2 | 3 | 4 | 5 |
|---|---|---|---|---|---|
| Cost (£) | 4 | 8 | 12 | 16 | 20 |
8 pens cost £10.
Draw the graph. Find the cost of 6 pens.
| Pens | 2 | 4 | 6 | 8 |
|---|---|---|---|---|
| Cost (£) | 2.50 | 5 | 7.50 | 10 |
5 litres of paint cost £20.
Draw the graph. Find the cost of 3 litres.
| Litres | 1 | 2 | 3 | 4 | 5 |
|---|---|---|---|---|---|
| Cost (£) | 4 | 8 | 12 | 16 | 20 |
6 m of rope costs £9. Draw the graph. Find the cost of 4 m.
| Metres | 2 | 4 | 6 |
|---|---|---|---|
| Cost (£) | 3 | 6 | 9 |
5 litres of paint cost £20.
Draw the graph. Find the cost of 3 litres.
| Litres | 1 | 2 | 3 | 4 | 5 |
|---|---|---|---|---|---|
| Cost (£) | 4 | 8 | 12 | 16 | 20 |
4 hours of parking cost £7. Draw the graph. Find the cost of 3 hours.
| Hours | 1 | 2 | 3 | 4 |
|---|---|---|---|---|
| Cost (£) | 1.75 | 3.50 | 5.25 | 7 |
5 litres of paint cost £20.
Draw the graph. Find the cost of 3 litres.
| Litres | 1 | 2 | 3 | 4 | 5 |
|---|---|---|---|---|---|
| Cost (£) | 4 | 8 | 12 | 16 | 20 |
5 kg of flour costs £4. Draw the graph. How many kg for £2.40?
| kg | 1 | 2 | 3 | 4 | 5 |
|---|---|---|---|---|---|
| Cost (£) | 0.80 | 1.60 | 2.40 | 3.20 | 4 |
Answer sheet
A graph for changing pounds to euros goes through (20, 23). How many euros is £50?
57.50 eurosA straight line goes through (4, 9) and (10, 22). Is it direct proportion? How do you know?
NoGraph A is a straight line through (0, 3) and (6, 15). Graph B is a curve through (0, 0) and (2, 4). Graph C is a straight line through (0, 0) and (5, 8). Which graph shows direct proportion?
C
Which graph shows direct proportion?
BThe graph shows the cost of sand. Use it to find the cost of 6 kg.
£15A straight line goes through (2, 6) and (5, 14). Does it show direct proportion? Explain.
No: 6 ÷ 2 = 3, 14 ÷ 5 = 2.8