Abigail and Mason are saving money to buy a CD that costs
nine dollars. Abigail has thirty dimes. Mason has three
dollar bills. Mason thinks that since he has ten times as
much money as Abigail, she needs to save all the rest of the
money needed to buy the CD. Abigail disagrees. Abigail
thinks they both have the same amount of money. Abigail
thinks it would be fair if they each saved half of the money
needed to buy the CD. Who is correct, Abigail or Mason?
Show all of your mathematical thinking.