Baseball Cards
Kevin, Dustin, and Mike collect baseball cards.



Together Dustin and Kevin have 81 cards.
If Dustin and Mike combined their cards, they would total 96.
The sum of Kevin's and Mike's cards is 93.
Question: How many cards does each boy have? Use the space below to explain
your answer and how you know it works.
Extra: The boys want to store their cards in albums. The pages hold 9 cards each.
How many pages will each boy need to hold his current collection?
Explain your response.
Expected Solution
The answer is Dustin = 42 cards, Kevin = 39 cards, and Mike = 54 cards.
Extra: Dustin = 5 pages, Kevin = 5 pages, and Mike = 6 pages
Student Response: When I solved this problem, I started by writing down all the facts of
the question I know.
D+K=81
D+M=96
K+M=93
Next I compared D+K=81 and D+M=96 and found out that M and K are 15 away from
each other by doing 96-81=15. Then I did the same steps for D+M=96 and K+M=93 and
found out that D and K are 3 away from each other. Then I tried to get near the middle
of 81. The numbers 40 and 41 are in the middle but you can't use those numbers
because they are not 3 apart. So I tried a different number that would be 3 apart and
add the 1's place of each number so it adds up to 11. I chose 11 to try to get 81, so I
tried 42 and 39 because those numbers are 3 apart and they add up to 81. Then I
subtracted 42 from 81 to try to figure out Mike's number of cards and got 54. After
that I added 54 and 39 to see if the sum would be 93 and I was right. To see if I was
correct I replaced the letters with the numbers and I got:
D+K=81 to 42+39=81
D+M=96 to 42+54=96
K+M=93 to 39+54=93
And the facts were correct.
Extra:
Each page holds 9 cards, so I divided the number of cards each person has by 9.
Dustin: 42/9= 4 remainder 6 but it would be 5 pages because the remainder will be in
the 5th page.
Kevin: 39/9= 4 remainder 3 but it would be 5 pages because the remainder will be in the
5th page.
Mike: 54/9=6, so it would be 6 pages.