Question 824440
If two fractions are equal, then they are said to be in proportion.

Suppose you have two boxes of red and white balls.  In the first box is one red and three white, so the fraction of red balls is 1/3 (one red with a total of three balls.  The other box has two red and 4 balls, so the fraction of red balls is 2/6 (two red with a total of 6 balls).

We want to see if the two fractions are in proportion

2/6 can be reduced to 1/3, so the two fractions are in proportion, but

if I add one red ball to the second box, then we see that 1/3 is not equal to 3/7.

we now see, that these fractions are in proportion

1/3, 2/6, 3/9, 4/12, 5/15   and so forth