standard_description: Use addition to find the total number of objects arranged in rectangular arrays with up to 5 rows and up to 5 columns; write an equation to express the total as a sum of equal addends.
problem_activity: Task
The table below shows all the products of pairs of numbers between 1 and 9.
[IMG]
Which numbers appear only once in the table of products?   Where are these numbers located in the table?  Why?
Which numbers appear the most frequently in the table?  Why?
Which numbers between 10 and 20 do  not  appear in the table?  What do these numbers have in common?


aligns: no