ratioProportion · Year 7 · Suggested learning sequence
Writing a ratio
A ratio compares two quantities. If a bag holds 6 red counters and 4 blue counters, the ratio of red to blue is 6 to 4, written 6:4. The order matters: 'red to blue' puts the red count first, so 6:4 and 4:6 are not the same. A ratio compares one part with the other part, not a part with the whole group — the 4 is the number of blue counters, not the 10 counters altogether. You read the two counts straight off and write them in the order the question names them.
Sample questions
A bag holds 3 red counters and 5 blue counters. Write the ratio of red to blue.
- Count each colour: 3 red, 5 blue.
- A ratio of red to blue lists the red count first.
- So the ratio of red to blue is 3:5.
Answer: 3:5
A bag holds 1 red counters and 4 blue counters. Write the ratio of red to blue.
- Count each colour: 1 red, 4 blue.
- A ratio of red to blue lists the red count first.
- So the ratio of red to blue is 1:4.
Answer: 1:4
A bag holds 4 red beads and 2 white beads. Write the ratio of red to white.
- Count each colour: 4 red, 2 white.
- A ratio of red to white lists the red count first.
- So the ratio of red to white is 4:2.
Answer: 4:2