6 CHALLENGE You and your friend are talking about your solutions to problem 2. Your friend said that there are exactly 12 different pairs of numbers with a difference of 12 and that he had found them all. How would you respond to him? 7 CHALLENGE You and your friend were thinking about pairs of whole numbers that have a sum of 12. How many pairs of whole numbers can you find that have a sum of 12? (Note: A whole number is equal to or greater than 0 and does not include a fraction. 2 is a whole number. 2 is not a whole number.) 8 CHALLENGE How many pairs of whole numbers have a sum of 40? 9 CHALLENGE How many pairs of whole numbers have a sum of 110? 10 CHALLENGE How many pairs of whole numbers have a sum of 99? The Math Learning Center | mathlearningcenter.org