Main content

## 3rd grade

### Course: 3rd grade > Unit 11

Lesson 3: Perimeter word problems# Perimeter word problem: skating rink

Solve a word problem involving perimeter of a rectangle. Created by Lindsay Spears.

## Want to join the conversation?

- Try to do this: 20+40+20+40 </>/= (40+20)x2 </>/= 40x2+20x2(4 votes)
- The answer to this question is 120=120=120(18 votes)

- Guys, Upvote for me.(10 votes)
- if you have 100,000,000,000 for your total length and width of the shape what would be the perimeter of that shape.(4 votes)
- The perimeter of a polygon is the sum of the lengths of its sides, so if we know all the side lengths we just add them together to find the perimeter.

The shape you're describing seems to be a square with side length 100,000,000,000, in which case the perimeter would be

100,000,000,000 + 100,000,000,000 + 100,000,000,000 + 100,000,000,000 =

= 400,000,000,000(4 votes)

- wow I totally get this now(4 votes)
- can i get a hoya(3 votes)
- everything is hard(3 votes)
- what if your not trying to find out the outside, and your trying to find the perimeter of the inside(0 votes)
- Good question! Finding how much could fit on the inside is called the area, and that is found by multiplying the length and width. If you are just talking about the lines on the inside (ex. where the two tables meet) then you could technically do that just like you do on the outside, but from what I know as someone in Algebra, you are probably not going to be asked to do this because the more you think about it, you could technically draw lines anywhere inside of the shape because it would not affect anything.(6 votes)

## Video transcript

- [Voiceover] Gus plans
to install a handrail around a skating rink. The rink forms a 40 meter
by 20 meter rectangle. How many meters of handrail does Gus need? So here's what we know
about the skating rink. It's a 40 meter by 20 meter rectangle. So let's draw the skating rink. That might help us to visualize, and we know that one
side length is 40 meters and another side length is 20 meters. So Gus definitely needs to put
some handrails 40 meters here and 20 meters here,
but that is not enough. As somebody who doesn't know how to skate, I very much hope Gus puts
handrail on this length and this length also. He needs to put the handrails
all the way around the outside where what we could call
the perimeter of the shape, the entire distance around the outside. Because the skating rink is a rectangle, we know that opposite sides are equal. So if this length is 40 meters up here, then this length down here
must also be 40 meters. And we can do the same thing with 20. If we have 20 over here,
then the length across must also be 20 meters. So now we can figure out the entire amount of handrail Gus needs, the
amount of meters he needs to buy to put around the skating rink. For this first side here,
he needs 40 meters plus to go down this side, he'll need another 20 meters of handrail. Going across the bottom of the rink, he'll need another 40 meters of handrail, and then, going up the side, he'll need another 20 meters of handrail. So we can add these to find
the total amount he needs. 40 plus 20 is 60. Then 60 plus 40 plus 40 is 100, and 100 plus 20 more is 120 meters. So to go the entire
distance around the outside of the skating rink, or the
perimeter of the skating rink with handrail, Gus will
need 120 meters of handrail.