## Finding the surface area of a rectangular prism

rectangular prism what we want to do is

we're going to find the total area of

the object meaning I want to find the

area of this front face this top face

the bottom face which is you can't see

this right side the left side and the

far back side all right so I want to

find the area every single one of them

and I want to add them all up and then

all combined is going to give me the

surface area so beside before we start

even doing our calculations the first

thing I'll do is well how many sides to

a half I have a front and back that's

two I have a right and a left

that's four and I have a bottom and a

top that's gonna be six and then one

thing that's important you guys then

remember since we're doing the

rectangular prism just like you know the

rules are erecting later you'd have to

opposite and equal sides the exact same

thing is going to be true with your when

you're doing the prism the right side is

going to be exactly the same as the left

side the top is going to be exactly the

same at the bottom and the front is

going to be exactly the same as the back

so what I can do is rather than trying

to calculate both of them I can just

multiply one of them by two so what I'll

do is I'll say two times the front slash

back

now the area of the front back plus two

times the let's do the right last left

side and that's area again plus two

times the bottom the top

and what that equals is service there

all right so let's do this first thing

we got to look at is how we're gonna

find out what is the area of the front

well the area of the front and the back

which are exactly the same is gonna be

15 times 9

because remember my rectangle is going

to be length for a rectangle or you know

it's going to be your length on your

wish so I have 15 times 9 is going to

give me 134 then hearing the right and

the left will the right side and left

side are a 9 by 9 rectangle which we

like to call a square 9 times 9 is 81

and the bottom of the top are also going

to give me 134

but remember I have to multiply each one

of these by two so what I'm gonna look

like is 2 times 1 34 plus 2 times 81

plus 2 times one thirty four two times

one thirty-four is a 268 Plus this give

me 162 plus 268 so to do all this in

the head so I'm just gonna make sure

that we do it all correctly just like

you learned back in the day you can do

I'll could probably go and give my best

estimates quickly but just to make sure

if you guys don't have a calculator if

you can't you know figure out head you

can always write it down like you first

learned 8 plus 8 is 16 plus 2 is 18 this

gives me 19 2 4 5 6 698 is resurfacing

so SERPs it equals 698

eldane yes we're so I'm market that all

the way down and all the pallets little

sloppy but just remember we're doing the

surface area to make sure you find every

single side and if your deal with a

rectangular prism or something that's

going to have you know symmetrical sides

you don't need to find the value of

every side you can just multiply those

same sides by to you know get the exact

same answer so that's a viable surface

area of a rectangle person