Problem Solving Strategy
Guess and Check
Objective Use the guess and check strategy to solve problems.
CA Standards
MR 2.0 Students use
strategies, skills, and concepts in
finding solutions.
NS 2.0 Students calculate
and solve problems involving
addition, subtraction,
multiplication, and division.
Also KEY NS 2.1 ,
KEY NS 2.2 , NS 2.8, MR 1.1,
MR 1.2, MR 2.3, MR 2.4,
MR 3.0, MR 3.1, MR 3.2,
MR 3.3
Lin and Farha took a trip to Chinatown. Lin took 6 times
the number of photos that Farha did. If they took a total
of 28 photos, how many photos did they each take?
UNDERSTAND
You need to find the number of photos each girl took.
The girls took 28 photos. Lin took 6 times as many
photos as Farha did.
PLAN
You can guess and check to find the answer.
Guess the number of pictures Farha took. If your guess
does not work, use it to make a better guess.
SOLVE
1st Guess: 6
Multiply: 6 × 6 = 36
Check: 6 + 36 = 42
42 > 28
Guess again.
Use a smaller number.
2nd Guess: 3
Multiply: 3 × 6 = 18
Check: 3 + 18 = 21
21 < 28
Guess again.
Use a larger number.
3rd Guess: 4
Multiply: 4 × 6 = 24
Check: 4 + 24 = 28
This guess is correct. Farha took
4 pictures and Lin took 24 pictures.
LOOK BACK
Check: 24 is 6 times the number of pictures Farha took.
4 + 24 = 28, the total number of pictures taken.
156
Houghton Mifflin California Math, Lesson Transparency 7.5
Copyright © Houghton Mifflin Company. All rights reserved.
Use with Chapter 7, Lesson 5
Solve using the Ask Yourself questions.
1. Mato went to a butterfly festival at the San Diego
Zoo. He saw these pictures of the butterfly and the
moth with the greatest wingspans. The total length
of their wingspans is 58 centimeters. The moth’s
wingspan is 2 centimeters longer than the butterfly’s
wingspan. What is the wingspan of each?
58 cm
Queen Alexandra’s Birdwing
Atlas Moth
Math Talk
How can you use your first guess to make a
better second guess?
Houghton Mifflin California Math, Lesson Transparency 7.5
Copyright © Houghton Mifflin Company. All rights reserved.
Use with Chapter 7, Lesson 5
• What facts do I know?
• How can I use my
first guess to make a
better second guess?