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Worksheet Grade 3 Math

Clovermead Wetland Beds: A Grade 3 Missing Side Worksheet

A grade 3 worksheet where students find perimeters and then work backward to a missing side length for the rectangular treatment beds of a fictional town wetland.

Objectives

  1. Students will find the perimeter of a rectangle when both side lengths are given.
  2. Students will find an unknown side length of a rectangle when the perimeter and one side are given.
  3. Students will compare two rectangles that share a perimeter but have different side lengths.

Vocabulary

Wetland
A wetland is an area like a marsh or swamp where the ground is soaked with water for much of the year. Wetlands soak up floodwater, help clean it, and shelter many kinds of animals.

Also: perimeter, rectangle, side length, bed

Teacher overview

Some towns finish cleaning their used water in a built wetland, a set of shallow rectangular beds planted with reeds, with a low rail around each bed to keep visitors on the path. Clovermead is a fictional town, and every bed size on this worksheet was chosen for the mathematics rather than measured at a real site. Students first find perimeters from given side lengths, then work backward from a known perimeter to a missing side. The error this worksheet is built to catch is subtracting only one length instead of two when working backward, which happens when a student forgets that a rectangle has two long sides and two short ones.

Clovermead Wetland Beds: A Grade 3 Missing Side Worksheet — Grade 3 Math
Name: ____________________________ Date: ______________

Student Worksheet

The town of Clovermead cleans water in a wetland. The wetland has beds shaped like rectangles. A rail goes all the way around each bed. All lengths are in meters.

  1. Bed A is 9 meters long and 6 meters wide. What is the perimeter of Bed A?
  2. Bed B is 12 meters long and 4 meters wide. What is the perimeter of Bed B?
  3. Bed C is a square. Each side is 7 meters. What is the perimeter of Bed C?
  4. Bed D has a perimeter of 40 meters. Bed D is 15 meters long. How wide is Bed D?
  5. Bed E has a perimeter of 26 meters. Bed E is 8 meters long. How wide is Bed E?
  6. Bed F is a square. Its perimeter is 36 meters. How long is each side of Bed F?
  7. Bed G is 10 meters long and 5 meters wide. Bed H is 11 meters long and 4 meters wide. Do the two beds have the same perimeter? Show how you know.
  8. The crew has 44 meters of rail. Bed J is 14 meters long and 8 meters wide. Is there enough rail to go all the way around Bed J?
  9. Bed K is 13 meters long. Its perimeter is 34 meters. How wide is Bed K?
  10. Tell how you can find a missing width when you know the perimeter and the length.

From Water for Schools (waterforschools.org). This material is in the public domain (CC0) and may be copied, edited, and shared freely.

Answer Key
  1. Answer: 30 meters.
    The two long sides are 9 + 9 = 18 meters and the two short sides are 6 + 6 = 12 meters, so the perimeter is 18 + 12 = 30 meters.
  2. Answer: 32 meters.
    The two long sides are 12 + 12 = 24 meters and the two short sides are 4 + 4 = 8 meters, so the perimeter is 24 + 8 = 32 meters.
  3. Answer: 28 meters.
    A square has four equal sides, so the perimeter is 7 + 7 + 7 + 7 = 28 meters.
  4. Answer: 5 meters.
    The two long sides use 15 + 15 = 30 meters, leaving 40 − 30 = 10 meters for the two short sides, and 10 ÷ 2 = 5 meters wide.
  5. Answer: 5 meters.
    The two long sides use 8 + 8 = 16 meters, leaving 26 − 16 = 10 meters for the two short sides, and 10 ÷ 2 = 5 meters wide.
  6. Answer: 9 meters.
    A square has four equal sides, so each side is 36 ÷ 4 = 9 meters.
  7. Answer: Yes.
    Bed G has a perimeter of 10 + 10 + 5 + 5 = 30 meters and Bed H has a perimeter of 11 + 11 + 4 + 4 = 30 meters, so the two beds match even though their sides differ.
  8. Answer: Yes.
    Bed J has a perimeter of 14 + 14 + 8 + 8 = 44 meters, which is exactly the length of rail the crew has, so the rail fits with none left over.
  9. Answer: 4 meters.
    The two long sides use 13 + 13 = 26 meters, leaving 34 − 26 = 8 meters for the two short sides, and 8 ÷ 2 = 4 meters wide.
  10. Answer: Subtract the length twice from the perimeter, then divide what is left by 2.
    Accept any wording that both takes away two lengths and then splits the rest into two equal widths.

Differentiation

Support

Give students a sketch of each bed with the four sides drawn and two of them already labeled, so the second pair of matching sides is visible before any adding starts. Provide a fill-in strip that reads "long + long + wide + wide = perimeter" for items 1 through 3. Allow color tiles or square grid paper so students can build the smaller beds and count around the outside.

Extension

Ask students to design a bed with a perimeter of 30 meters whose sides are different from both Bed G and Bed H, and prove the perimeter with an equation. Have them find every rectangle with whole-meter sides that has a perimeter of 20 meters, list them in order, and describe the pattern they notice in the pairs.

ELL supports

Pre-teach "perimeter," "rail," "bed," and "width" with a labeled drawing of one rectangle with arrows tracing all the way around the outside. Provide the sentence frame "Two sides are ___ meters and two sides are ___ meters, so the perimeter is ___ meters." Let students trace around each bed with a finger before writing anything.