The problem requires us to express the ratio of cats to dogs in a pet store in its simplest form. There are 21 cats and 6 dogs. We need to simplify the ratio $21:6$.

1. Problem Description

The problem requires us to express the ratio of cats to dogs in a pet store in its simplest form. There are 21 cats and 6 dogs. We need to simplify the ratio $21:6$.

2. Solution Steps

To simplify the ratio, we need to find the greatest common divisor (GCD) of 21 and

6. The factors of 21 are 1, 3, 7, and

2

1. The factors of 6 are 1, 2, 3, and

6. The greatest common divisor of 21 and 6 is

3.

Now, we divide both numbers in the ratio by their GCD.

$21 \div 3 = 7$

$6 \div 3 = 2$

Therefore, the simplified ratio is $7:2$.

3. Final Answer

The ratio of cats to dogs in simplest form is 7:2.