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Tide-Pool Survey: Reconstruct the Counts

Solve tide-pool survey problems with two-step equations, interpret unknowns, and compare algebraic steps with arithmetic solutions.

Grade 7MathInteractive · Printable

Aligned to7.EE.B.4.a

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What’s included

Single worksheet
Auto-graded online
1 Common Core standard
Printable answer key
13 questions
Classroom-ready

Details

Format: Interactive · Printable
Grade: Grade 7
Subject: Math
Question types: Fill in the blank, Multiple choice, Circle the answer, Short answer

About this worksheet

What students practice

Students model field-survey situations with equations of the forms px + q = r and p(x + q) = r.
Students solve equations with rational coefficients and interpret solutions in context.
Students compare algebraic steps with arithmetic methods for solving word problems.

How to use

Use after introducing two-step equations. Have students show their calculations beside each problem, then discuss how grouping changes the arithmetic solution.

Curriculum

Common Core standard covered

7.EE.B.4.a

Solve word problems with equations like px + q = r and p(x + q) = r, and compare the algebra with an arithmetic solution.

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Tide-Pool Survey: Reconstruct the Counts

Use equations and arithmetic to recover missing field-trip records.

Recover the Field Records

Each problem describes a separate survey during a marine biology field trip. Model the situation and find the missing information.

Students counted the same number of limpets in each of 7 marked survey squares. They also counted 11 limpets outside the squares. Their total was 95 limpets.

How many limpets were in each square? limpets

Each of 3 tide pools contained x snails and 8 crabs. Students counted 69 animals altogether. Which equation represents this record?

A. 3(x + 8) = 69
B. 3x + 8 = 69
C. 8(x + 3) = 69
D. 3(x − 8) = 69

Four student teams each counted an equal number of shore crabs. A guide counted 9 more crabs in a separate area. Their combined count was 53. The equation is 4x + 9 = 53. What does x represent?