Elementary Test Prep Math 4 (Grade 3) Guess and Check

Trial and Error
Lesson
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There are many ways to solve
a math problem.
Sometimes the best strategy is to
"Guess and Check".

                            Problem Solving Process
                       Step 1: Understand the problem.
                       Step 2: Make a plan.

Choose a strategy.
                                     "Guess and Check"
                       Step 3: Carry out the plan.
                       Step 4: Look Back.

Use "Guess and Check" to solve these problems.

Lilly made 7 place cards for
her party. She needs a total
of 12 place cards.
How many more does she
need?

Step 1: How many more place cards
does Lilly need?

Step 2: Try different answers to see
             what works.
Step 3: 7 +□= 12
             Try numbers in the equation.
                Does 7 + 3 = 12? No, 7 + 3 = 10
                Does 7 + 4 = 12? No, 7 + 4 = 11
                Does 7 + 5 = 12? Yes!

Step 4: 7 + 5 = 12
Lilly needs 5 more place cards.

Tom wants to buy a pen at
the school store.
The pen costs $.50.

He takes 1 quarter
and 1 dime

and 1 nickel
from his pocket.

What other coin does he
need?

Step 1: What coin does Tom need to
add to a quarter, a dime and a
nickel to total $.50?

Step 2: Try different coins to see
             what works.

Step 3: $.25 + $.10 + $.05 = $.40
                 $.40 +□= $.50
             Try coins.
              Does $.40 + = $.50?
                      No,   $.40 + = $.41
                Does $.40 + = $.50?
                      No,   $.40 + = $.45
                Does $.40 + = $.50? Yes!

Step 4: $.40 + = $.50
Tom needs 1 more dime.

Ben's baseball team is ahead by a
score of 7-3.

How many runs must the other
team score to tie the game?

Step 1: By how many runs is Ben's
team winning?

Step 2: Try different answers to see
             what works.
Step 3: 3 +□= 7
             Try numbers in the equation.
                Does 3 + 2 = 7 ? No, 3 + 2 = 5
                Does 3 + 3 = 7 ? No, 3 + 3 = 6
                Does 3 + 4 = 7 ? Yes !

Step 4: 3 + 4 = 7
The other team needs to
score 3 runs to tie the game.

Remember:

"Guess and Check" is one strategy to use in problem solving.

Click on the pencil for practice.

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