Copy and complete each of the Diamond Problems below. The pattern used in the Diamond Problems is shown at right.

1. 

   Hint (a):

   Add $x$ and $y$ to get the sum. Multiply $x$ and $y$ to get the product.

   Answer (a):

   

2. 

   Hint (b):

   Follow the pattern shown above right.

3. 

   Hint (c):

   $5+ y = 5 + a$
   What is $y$?

   Answer (c):

   The product is $5a$.

4. 

   Hint (d):

   $0.99 − 0.90 = 0.09$