Write two fractions where the lcd is 20, but the product of the denominators is not 20

and  

Step-by-step explanation:

To calculate the Least Common Denominator (LCD) of two fractions you must descompose each denominators into their prime factors and multiply the commons and non-commons with the largest exponent.

Let's write the following two fractions:

and  

The LCD is:

So, we have two fractions where LCD is 20.

Let's verify that product of the denominators is not 20:

(The product is not 20).