Perimeter and area of a rectangle. Also, circumference.?

Question

Okay, so I completely forgot how to do the area and perimeter of rectangles when the length and width are a number such as 8x.

For example, one rectangle's length is 8x, and width is 2x.... I figured to find the area you multiply LxW and get 16x squared...?

But how do you find the perimeter of that rectangle?

Also, how would you find the circumference of a circle that's radius is 3x, and it's area? The x's are really throwing me off....

please help.

Answer 1

Perimeter and circumference are the measure of the exterior distance for any polygon and circle.  The x just represents any given unit of measuere be it inches or meters, feet, or yards.

You just add up the sides for Perimeter.  Area is length times width for rectangles.  So in you example, 8 is the length and 2 is the width.

There are two lenths and 2 widths for the perimeter.  Here the perimete is 20.  The area is simpley width times length or 16 square units so you know that one.

In a circle, the circumference is two times the radius times Pi.  Pi is like 3.14159 26535 something but most high schools will just use 3.14 or 3.142. ( i cant remember past those digits.  three point one four one five nine is like a phone number.  when I was 26 i wanted to buy a BMW 535)  

OK so circumference is (3r plus 3r) times pi or 2*r*Pi.  it is like almost 19 units..  you can do the multiplication.

Area is a bit tricky to remember becaue it is Pi * r times r.

3*3*3.14159 is almost 28 square units.

Remember Circumference is  two pie r

and area is pie r squared.

Answer 2

1) Perimeter P (rectangle) = 2L + 2W

So, for the ablove example you would have

P = 2(8x) + 2(2x) = 16x + 4x = 20x

2) Circumference C (circle) = 2 * pi * r

Hence, for the ablove the example, you have

C = 2 * pi * 3x = 6x * pi

A = pi * r^ 2

A = pi (3x)^2

A = (9x^2) * pi

Answer 3

Your answer for area is correct.

the formula for perimeter of a rectangle is 2(L + W)

so for this problem it is 2(8x + 2x) = 2(10x) = 20x

for the circle:

P = 2pir = 2(pi)3x = 6(pi)x

A = (pi)r^2 = (pi)(3x)^2 = 9pix^2

Hope that helps!

Answer 4

Perimeter = 2(x+y)

in ut example 2(8+2) = 20.

circumfrence issame as perimeter, but it is for circle

= 2Pi r

2* 22/7 * 3 =18.85

Oh its been such a long time since i left maths

Answer 5

Area where length is 8x and width is 2x:

= 8x(2x)

= 16x²

Answer: 16x² is the area.

Perimeter in your previous example:

= 2(8x + 2x)

= 2(10x)

= 20x

Answer: 20x is the perimeter.

Circumference of the circle (p = 2 * r * 3.14159):

= 2 * 3x * 3.14159

= 18.84954x

Answer: 18.84954x is the circumference

Formula: 2 * radius * pi

pi = 3.14159 or 3.14