Perimeter as the distance all the way around a shape. Your child counts unit lengths around grid shapes, tells perimeter from area, and adds side lengths in stories.
Start at one corner and walk around the outside edge, counting each unit length once until you're back at the start. Or add up all the side lengths.
perimeterthe distance all the way around a shape
sideone straight edge of a shape
unitthe length you count by
areathe space inside a shape
Watch for: Counting the squares inside (the area) instead of the edges around. Counting a corner square once when it has two outside edges. Adding only two sides of a rectangle: a 12 by 6 card needs 12 + 6 + 12 + 6.
At home: Walk the edge of a rug, table or room, counting steps or measuring with string. Then ask how you'd find the space it covers instead.
Sample sheet and answer key
Luna's Space Adventure
Grade 3 · Perimeter as distance around · 3.GR.C.8
NameDate
Astronaut Luna is exploring a far-off corner of space. Solve each problem to help Luna's mission go smoothly!
Walk around the shape
Count the unit lengths all the way around. That is the perimeter.
units
units
units
units
units
units
Around or covering?
Perimeter goes around the edge. Area covers the inside.
a frame around a photoperimeterarea
a rug on the floorperimeterarea
a path around a pondperimeterarea
grass for a fieldperimeterarea
trim around a windowperimeterarea
a cloth on a tableperimeterarea
All the way around
1
Nova glues ribbon all the way around a card 18 cm long and 8 cm wide. How much ribbon does Nova need?
cm
Sheet
Luna's Space Adventure
Grade 3 · Perimeter as distance around · 3.GR.C.8
Answer key
Astronaut Luna is exploring a far-off corner of space. Solve each problem to help Luna's mission go smoothly!
Walk around the shape
Count the unit lengths all the way around. That is the perimeter.
10units
16units
16units
12units
18units
16units
Around or covering?
Perimeter goes around the edge. Area covers the inside.
a frame around a photoperimeterarea
a rug on the floorperimeterarea
a path around a pondperimeterarea
grass for a fieldperimeterarea
trim around a windowperimeterarea
a cloth on a tableperimeterarea
All the way around
1
Nova glues ribbon all the way around a card 18 cm long and 8 cm wide. How much ribbon does Nova need?
18 + 8 + 18 + 8 = 52
52cm
Answer key
New problems every time, three levels (gentle, core and stretch), themes to pick from, a second page if you want one. Each sheet comes with an answer key and a one-page guide for grown-ups.
