– [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.

Perimeter word problem (skating rink) | Math | 3rd grade | Khan Academy
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One thought on “Perimeter word problem (skating rink) | Math | 3rd grade | Khan Academy

  • June 14, 2016 at 6:20 pm
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    Does This Channel Only Do 3 Grade?

    Reply

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