What is the ratio 15/45 expressed in simplest form?

To find the simplest form of a fraction, you have to find the greatest common factor (GCF). To do so, list out the factors of the numerator (15) and the denominator (45) and find the biggest common number between the two numbers.

Factors of 15: 1, 3, 5, 15
Factors of 45:  1, 3, 5, 9, 15, 45

Out of those factors, we can see that 1, 3, 5, and 15 are the common factors, but 15 is the greatest which makes it our GCF. 

Now we can divide the numerator and the denominator by the GCF to receive our simplest form.

15 ÷ 15 = 1
45 ÷ 15 = 3

Rewrite the fraction with the new numerator (1) and the new denominator (3).

The simplest form of 15/45 is: 1/3 or 0.3333.