TEKS 4.5D · Grade 4

Perimeter and area of rectangles

Working out the distance around a rectangle and the space inside it, and telling the two apart.

The standard itself reads: “4.5D: solve problems related to perimeter and area of rectangles where dimensions are whole numbers”

One of them, worked all the way through

1. Area is the space inside. Cover the rug in one-foot squares: 5 rows of 7, so 7 x 5 = 35 square feet.
2. Perimeter is the walk around the edge: 7 + 5 + 7 + 5 = 24 feet.
3. Same rug, two different questions, two different answers.

This is one way, not the only way. The printable shows the same question worked more than one way, because children get there differently.

What usually goes wrong, and what helps

Each of these is a different misunderstanding rather than a slip, so each one needs something different. Find the one that sounds like your kid.

The student adds the two sides instead of multiplying them

Ask whether they are counting squares inside or steps around the edge. Squares multiply.

The student finds the distance around when the question asked for the space inside

Trace the edge with a finger for perimeter. Sweep a palm across the middle for area.

The student adds only the sides that are labeled and forgets the two that are not

A rectangle has four sides and only two of them get labels. Write the other two in before adding anything.

The student answers in the wrong unit: feet where it should be square feet

Feet measure the edge. Square feet count the squares inside. The unit says which question got answered.

Try this at home

Walk the edge of a rug with your finger for perimeter, then lay a hand flat on it for area. Same rectangle, two different questions, and mixing them up is the single most common mistake on this standard.

where these methods come from The strategies behind it: the Area chart and the Perimeter chart.

What’s in the printable

Four questions on this skill, two to a page. The rest of the file is for the adult: an answer key, a worked solution for every question, and teacher pages on what each wrong answer means. 10 pages in all.