Which ages is this activity for?

It is designed for Grade 3 (Measurement & Data) and works well for whole-class, small-group, or independent practice.

The Mending Fences — Perimeter: the Distance Around (Grade 3)

A free interactive Grade 3 math activity: help Hazel the badger mend the paddock fences and tell fencing the edge from planting the grass inside. Perimeter is the distance all the way around a shape — a length, not the space it covers. Mend a missing fence board when you know the whole fence and one side, judge which field needs more fence but grows less grass, tell the around-the-edge marks from the squares inside, and check whether a roll of fence reaches around. Common Core 3.MD.D.8.

Grade 3·Measurement & Data·3.MD.D.8

About this activity

Hazel the badger has paddock fences to mend, and children pitch in by finding the missing board when the whole fence and one side are known — a 6-by-4 paddock needs a board of 4, not 14 or 8. Along the way they judge which field needs more fence but grows less grass, tell the marks around the edge from the squares inside, and check whether a roll of fence reaches all the way around, in a free, interactive Grade 3 math activity that plays right in the browser with no install and no account.

The big idea is that perimeter is the distance all the way around a shape — a length — and not the space it covers. The rounds deliberately pit fence against grass: a long, thin 9-by-2 field and a square 5-by-5 field invite children to compare the fence around with the grass inside and discover the two can disagree. By fencing the edge in some rounds and counting inside squares in others, children feel the difference instead of memorizing a rule.

It is aligned to Common Core 3.MD.D.8 — solving real-world problems involving perimeter, including finding an unknown side length and comparing shapes with the same perimeter or area. No timer, no score — just calm, playful practice.

What's inside this activity

Designed for Grade 3 learners (ages about 8–9)
Common Core strand: Measurement & Data
Aligned to Common Core standard 3.MD.D.8

How to play

Read the fence job — mend a missing board, compare two fields, or check whether a roll reaches around.

Work out the distance around the edge, then tap the answer that mends the fence.

Got it wrong? Try again as many times as you like — there is no timer and no score.

What your child practices

Find an unknown side length when the perimeter and one side are known
Tell perimeter (the distance around) apart from area (the space inside)
Compare fields with the same area but different perimeters
Check whether a given length of fence reaches around a shape

Learning goals

Solve perimeter problems, including finding an unknown side length — the focus of Common Core 3.MD.D.8

Understand perimeter as a length around a shape, distinct from area

Compare shapes that share a perimeter or an area

Frequently asked questions

What does the The Mending Fences — Perimeter: the Distance Around (Grade 3) activity teach?: The Mending Fences — Perimeter: the Distance Around (Grade 3) is a free interactive activity for Grade 3, focused on Measurement & Data. Children play it right in the browser — no printing, login, or setup required.
Is The Mending Fences — Perimeter: the Distance Around (Grade 3) free to use?: Yes. The Mending Fences — Perimeter: the Distance Around (Grade 3) is completely free, with no signup and no paywall, on any tablet, laptop, or classroom whiteboard.
Which ages is this activity for?: It is designed for Grade 3 (Measurement & Data) and works well for whole-class, small-group, or independent practice.

Practice this standard

See all 3.MD.D.8 activities