Ratio, proportion and rates of changeKS3 / GCSE

Recognising direct proportion from a graph

Recognise the graph of direct proportion.

  • In direct proportion, is constant.
  • Use , where is a constant.
  • The graph must be a straight line through the origin.

Example 1

Does this graph show direct proportion? Give a reason.

Yes

It is a straight line through the origin, so .

Example 2

Does this graph show direct proportion? Give a reason.

No

It is a straight line, but it does not pass through the origin.

Your turn

Question 1

Does this graph show direct proportion? Give a reason.

Check answer
Yes

It is a straight line through the origin, so .

Question 2

Does this graph show direct proportion? Give a reason.

Check answer
No

It is a straight line, but it does not pass through the origin.

Question 3

Does this graph show direct proportion? Give a reason.

Check answer
Yes

It is a straight line through the origin, so .

Question 4

Does this graph show direct proportion? Give a reason.

Check answer
No

It is a straight line, but it does not pass through the origin.

Question 5

Does this graph show direct proportion? Give a reason.

Check answer
Yes

It is a straight line through the origin, so .

← All Ratio, proportion and rates of change cardsReport a mistake