• Proprortions are equal ratios.
• If two ratios are equal, then four numbers forming the two ratios in order are said to be in proportion.

That is, if a:b = c:d, then a,b,c and d are said to be in proportion.

Proportion a:b = c:d is also denoted by a/b = c/d or a:b :: c:d and is read as
"a is to b as c is to d".

Example: Distance travelled in 4 hours is 200 miles, and distance travelled in 7 hours is 350 miles.
Ratio of times = 4:7
Ratio of distance travelled = 200:350, simplify this we get 4:7.
Therefore, Ratio of times = Ratio of distances
That is, 4:7 = 200:350