Do the ratios 19/8 and 5/4 form a proportion?

Explanation:

Your teacher is effectively asking "are the fractions 19/8 and 5/4 equal?"

Let's assume for now that they are. So we have 19/8 = 5/4

To check if that is a true equation, let's cross multiply

19/8 = 5/4

19*4 = 8*5

76 = 40

The last equation is not true, so the first equation is also not true. The ratios are not in proportion.

Alternative method:

Instead of cross multiplying, we can get all the fractions to have the same denominator. The LCD (lowest common denominator) of the two given fractions is 8. Let's turn 5/4 into a fraction with 8 in the denominator.

We'll multiply top and bottom by 2 to get 5/4 turning into 10/8

Now we're asking "are 19/8 and 10/8 the same?" in which the answer is "no they are not the same". The numerators 19 and 10 are different. The fraction 19/8 is larger than 10/8. So 19/8 is larger than 5/4.

2nd Alternative method:

Use your calculator to see that

19/8 = 2.375

5/4 = 1.25

The decimal values should be the same if the fractions were equal, but they are not. This is a very quick way to compare two fractions.