Lesson 5 - Area of a Circle #3

[One speaker] 

[question: A helicopter landing pad has a diameter of 28 meters. Find the radius of the landing pad and then find the surface area of the landing pad. Round your answer to the nearest whole number.]

Narrator: [reads question. Landing pad image appears] Okay, so here’s our landing pad, and it tells us that the diameter of the landing pad is 28 meters. So we know the diameter cuts straight across. So our diameter is 28 meters, but it asks us to find the radius and then use that to find the area.[d=28m] So the radius we know that the diameter is two times the radius. [d=2r] So half of our diameter will be fourteen. So our radius will be 14 meters. [r=14m]  Now we can use that and plug into our formula for the area, and find the area of our helicopter landing pad here. So the formula for the area of a circle is . we know that our radius is 14 meters, so we can plug that in. We have pi times 14 meters squared.[pulls up calculator] Fourteen squared, there’s a squared button up here or we can do times 14 again, I’m going to use the squared button. So 14 squared is 196. Let’s write that here, we have pi times 196 and our meters are squared as well. So we can write this as 196m squared, or we can multiple 196 times pi and see what we get. So we have 196 times pi equals, and so we get 615.75, and let’s see what we needed to round to. We needed to round to the nearest whole number. So looking back here at our calculator, we can see that we need to round to 616. So let’s write that right here, 616 meters squared. [196m2=616m2] So the area of our helicopter landing pad is 616 meters squared.

[End of video]