Definition
Ratio notation
Ratio notation writes an ordered comparison, such as 2:3, “2 to 3,” or 2/3.
What it means
Read the colon as “to.” The first number names the first quantity and the second number names the second quantity, so switching the order changes the comparison. Equivalent ratios can look different while describing the same relationship.
Remember it
A ratio keeps two quantities in labeled seats: first quantity, then second quantity.
Example
A box has 6 red counters and 4 blue counters. The ratio of red to blue is 6:4, which simplifies to the equivalent ratio 3:2. Blue to red would be 4:6, not 6:4.
Watch for
The colon in 3:45 on a clock is time notation, not automatically a ratio.
Common mix-up
Do not reverse the order: red to blue and blue to red are different ratios.
Exact meaning
Ratio notation represents an ordered multiplicative comparison of two quantities, commonly as a:b, “a to b,” or a/b when the context makes the compared quantities and units clear.