Multiplication Cluster
Problems
2.4
Guiding Questions
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How can solving easier problems help us find
the product of a multiplication problem?
How can estimating products help us judge the
reasonableness of an answer?
Consider This
Let’s tackle the following problem. For Field Day,
there will be 42 teams, with 19 students on a
team. We need to figure out how many students
will be playing so that the school can make a Tshirt for each player. How can we solve this ?
Solve these problems mentally. Think
of teams:
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42 x 10 =
42 x 5 =
42 x 2 =
42 x 20 =
Let’s consider 42 x 19 again. See if some of the
problems you just did mentally might help you
find the product of 42 x 19. Share!
Consider This!

We could use 42 x 20 to solve 42 x 19. This
would represent 20 teams with 42 on a
team…so there is one group of 42 too many.
Take away 42 from the answer, and that gives
you 19 teams of 42 instead of 20!
Cluster Problems 1 - 4. Solve the “cluster” problems
mentally, then solve the final problem below them.
How did the clusters help you solve the final?
10 x 12
20 x 12
20 x 10
8 x 10 28 x 2
Now solve 28 x 12. How did you solve it?
35 x 10
35 x 20
10 x 25 20 x 25
Now solve 35 x 25. How did you solve it?
10 x 21
20 x 20
20 x 21 5 x 21
Now solve 27 x 21. How did you solve it?
30 x 25
7 x 20
100 x 7
150 x 7
40 x 7
15 x 7
Now solve 146 x 7. How did you solve it?
Guiding Questions


How can solving easier problems help us find
the product of a multiplication problem?
How can estimating products help us judge the
reasonableness of an answer?