Chapter 12 Lesson 2
Perimeter and Area
How to change units with area.
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You'll like this lesson. It's all
about your favorite shape.
Squares? We've already
studied squares. Remember?
Squares
True. What do squares measure?
Got to be area. Why?
Yeah, but there are other
kinds of square units.
Squares are squares. You
can't mess around with squares.
Different Units
Relax. Were just changing
units. You know how to do that.
That means there's a basic fact.
Square Inches
We'll start with square inches.
How big is a square inch?
It's an inch on each side.
How many square inches
are in a square foot?
How do you find that?
12 Inches
12 Inches
Put 12 inches on a side.
Now, multiply them.
144
12 Inches
12 Inches
Yup. 12 x 12 is 144.
What's the label?
1 Square Foot =
144 Square Inches
1 square foot
is 144 square inches.
That sure is alot of little squares.
1 sq ft = 144 Sq Inches
2 sq ft = ? Sq Inches
If 1 sq foot is 144 square inches,
how many are in 2 square feet?
1 sq ft = 144 Sq Inches
2 sq ft = 288 Sq Inches
Easy, multiply 2
is 288 square inches.
1 sq ft = 144 Sq Inches
2 sq ft = 288 Sq Inches
Easy, he says.
We'll try the next one.
5 sq ft = ? Sq Inches
Now we'll find 5 square feet.
What's the base fact again?
1 sq ft = 144 Sq Inches
5 sq ft = ? Sq Inches
144 sq inches in a square foot.
1 sq ft = 144 Sq Inches
5 sq ft = ? Sq Inches
So, how do you find it?
5 x 144 = 720
5 sq ft = 720 Sq In
Multiply 5 x 144 for 720 sq inches.
Nice, now for the easier ones.
3 feet
3 feet
How many square feet
are in a square yard?
1 Square Yard =
9 Square Feet
3 x 3 is 9 square feet.
You want to draw a picture for it?
3 feet
3 feet
There's your 9 square feet.
Now we'll use
that to find another area.
2 feet
9 feet
Let's say a carpet is
9 feet long and 2 feet wide.
How many square yards is that?
2 feet
9 feet
Um, Mr G, it's in feet, not yards.
2 feet
9 feet
No problem.
What's the base fact?
18 Sq Ft = ? Sq yards
1 Sq Yard = 9 Sq Feet
1 square yard is 9 square feet.
18 Sq Ft = ? Sq yards
1 Sq Yard = 9 Sq Feet
It's upto you how to find it.
18 Sq Ft = ? Sq yards
1 Sq Yard = 9 Sq Feet
Well, it's backwards, so divide.
I know the answer.
18
9=2
Square yards
Divide 18 by 9
to get 2 square yards.
I'll change it a little bit.
20 Sq Ft = ? Sq yards
What if it's
20 square feet instead of 18?
20
2 x 9 = 18
2
Use the same fact, but now
you subtract to get 2 feet left.
I'll put it altogether.
20 Sq Ft = 2 Sq yds
and 2 sq ft
That makes it 2 square yards
and 2 square feet.
20 Sq Ft = 2 Sq yds
and 2 sq ft
Right, it works the same way
all the other basic facts did.
That's the problem.
More basic facts to remember.
I know. More
stuff to put in your brain.
Qs
What does
a square foot measure?
Square 1 Foot
Foot
1 Foot
A square foot is 1 foot
on each side. It finds area.
How many square inches
are in a square foot?
144
12 Inches
12 Inches
12 x 12 is 144, so
it's 144 square inches.
How many square feet
are in a square yard?
9
3 feet
3 feet
1 Square Yard =
9 Square Feet
Chapter 12 Lesson 2a
Perimeter and Area
Other units to measure area.
You know, I liked squares better
before we did all the square stuff.
And there's more. I'm
pretty sure you know this one.
Is it bigger than square yard?
Alot bigger.
I mean, a whole lot bigger.
Acre
The one we use
most is called an acre.
I know that, we live on 3 acres.
And mostly it's used for land.
I know it takes me 2 hours
to cut the grass on an acre.
Then you know how big an acre is.
There is an easy way to
think about how big an acre is.
1 Football Field
It's a football field
without the end zones.
Our land doesn't seem that
big, but we have lots of trees.
212 feet x 212 feet
You can think
about 212 x 212 feet.
How many square feet is that?
43,560 square feet
That's 43,560 square feet.
No wonder it
takes so long to mow.
I want you to get an idea of
how square feet are used.
This is going to be different.
1 small room
First, how many square feet
are in an average small room?
I don't know. I need
some more information.
1 room
10 x 10 feet
Ok, it's 10 feet by 10 feet.
How many square feet is it?
1 room
100 square feet
That's 100 square feet.
How about a bigger one?
That's pretty small.
1 large room
10 x 20 feet
Is that like a living room?
1 large room
10 x 20 feet
Yup, how many square feet?
Large Room
200 square feet
200 square feet sounds like alot.
Say you have a 6 room house
with 3 small and 3 large rooms.
How many square feet is that?
3 x 200 = 600 sq ft
4 x 100 = 400 sq ft
1000 sq ft
1000 square feet.
Is that like an average house?
1000 sq ft
In the 1950s it was average.
Guess how big average is now?
2400 sq ft
Wow! 2400 square feet
is alot bigger.
Yeah, but now there are huge
mansions. Guess how big.
10,000 sq ft
Oh, my gosh!
That's like 4 regular houses.
Let's go bigger. Here's the
largest house in the USA.
175,000 sq ft
What? That's not a house.
It's a whole school.
It used to be a house. Now
it's a museum. Here's a house.
90,000 sq ft
How many bathrooms does it have?
You'd only have 100
bathrooms to choose from.
I could use a different bathroom
everyday for 3 whole months.
Can you imagine playing hide
and seek in a place like that?
I'd probably get lost just
trying to find breakfast.
Yeah, you wouldn't want to
mow the lawn for that place.
I'd just get done mowing it
and have to start all over again.
I can't imagine the taxes
on a place that big.
Qs
What sports field is like an acre?
1 acre is about
1 Football Field
That's without the end zones.
Chapter 12 Lesson 2
Perimeter and Area
Short Lesson
How to change units with area.
Squares
Everything we've talked about
can be measured in squares.
How big is a square foot
piece of paper?
Foot
1 Foot
12 inches
1 Foot
That paper would
be 1 foot on all 4 sides.
We have a way to write that.
Square 1 Foot
Foot
1 Foot
It's 1 square foot.
What if we change
to an inch on each side?
Square Inch
Square 1 inch
Inch
1 inch
It's an inch on each side.
We'll use both units.
Square Foot =
? Square Inches
How many square inches
are in a square foot?
Think about what changes.
12 Inches
12 Inches
Change the foot to 12 inches.
How many square inches is it?
1 Square Foot =
144 Square Inches
That's 144 square inches.
Watch how fast it goes up.
1 sq ft = 144 Sq Inches
2 sq ft = ? Sq Inches
If 1 sq foot is 144 square inches,
how many are in 2 square feet?
1 sq ft = 144 Square In
2 sq ft = 288 Square In
Now we'll talk
about square yards.
Square Yards
How many square feet
are in a square yard?
3 feet
3 feet
It's 3 feet on each side.
How many square feet
are in a square yard?
3 feet
3 feet
There's 9 square feet.
Here's the basic fact for it.
1 Square Yard =
9 Square Feet
That's 9 square feet.
We'll make a problem for it.
2 feet
9 feet
A carpet is 9 feet long
and 2 feet wide.
How many square yards is that?
2 feet
9 feet
It's in feet, not yards.
How do you find any area?
9 x 2 = 18
square feet
Multiply 9 x 2 is 18 square feet.
How do you change
it to square yards?
18 sq ft = ? sq yd
Use a basic fact.
What basic fact is that?
18 sq ft = ? sq yd
1 sq yd = 9 sq ft
1 square yard is 9 square feet
How do you solve it?
18 sq ft = 2 sq yd
1
sq yd
= 9 sq ft
It's backwards, so
18 divided by 9 makes 2.
There is 1 more unit.
Acre
The one we use
most is called an acre.
Mostly, it's used for land.
How big is an acre?
1 Football Field
is about an acre.
That's without the end zones.
How many square feet are
in a square acre?
212 feet x 212 feet
Same as 212 x 212 feet.
How many square feet is that?
43,560 square feet
That's 43,560 square feet.
It's alot easier saying an acre
instead of 43,560 square feet.
Questions
12 Inches
12 Inches
How many square
inches are in a square foot?
144
12 Inches
12 Inches
Multiply 12 x 12 is 144.
144 square inches in 1 sq foot.
1 yard
1 yard
How many square feet
are in a square yard?
3 feet
3 feet
There's 9 square feet
in a square yard.
What sports field is like an acre?
1 acre is about
1 Football Field
That's without the end zones.
Chapter 12 Lesson 2
Perimeter and Area
Practice #1
How to change units with area.
1 yard
1 yard
How many square feet
are in a square yard?
3 feet
3 feet
There's 9 square feet
in a square yard.
12 Inches
12 Inches
How many square inches
are in a square foot?
144
12 Inches
12 Inches
Multiply 12 x 12 is 144.
144 square inches in 1 sq foot.
What sports field is like an acre?
1 acre is about
1 Football Field
That's without the end zones.
Problems
1 yard
3 yards
What's the 1st step to find
the square feet in 1 yd x 3 yd?
1 yard
3 yards
Find the square yards.
How many square feet
are in each one?
9
9
9
1 yard
3 yards
Each square yard
has 9 square feet.
What's the answer?
9
9
9
1 yard
3 yards
27 square feet.
Find the square yards
and multiply x 9.
1 yard
4 yards
How do you find the square feet
in a rectangle that's 1 yd x 4 yd?
1 yard
4 yards
Multiply 1 x 4 x 9
Why did it multiply x 9?
9
9
9
9
4 yards
Each square yard
has 9 square feet.
What's the answer?
1 yard
9
9
9
9
4 yards
36 square feet.
Find the square yards
and multiply x 9.
1 yard
Chapter 12 Lesson 2
Perimeter and Area
Practice #2
How to change units with area.
1 yard
1 yard
How many square feet
are in a square yard?
3 feet
3 feet
There's 9 square feet
in a square yard.
12 Inches
12 Inches
How many square inches
are in a square foot?
144
12 Inches
12 Inches
Multiply 12 x 12 is 144.
144 square inches in 1 sq foot.
What sports field is like an acre?
1 acre is about
1 Football Field
That's without the end zones.
Problems
1 ft
2 ft
What's the 1st step to find
the square inches in 1 ft x 2 ft?
1 ft
2 ft
How do you find the square inches
in a rectangle that's 1 ft x 2 ft?
1 ft
2 ft
Multiply 1 x 2 x what?
How many square inches
are in a square foot?
1 ft
2 ft
Multiply 1 x 2 x 144
Multiply 144. What's the answer?
1 ft
2 ft
288 square inches
2 square feet is 288 square inches.
1 ft
3 ft
How do you find the square inches
in a rectangle that's 1 ft x 3 ft?
1 ft
3 ft
Multiply 1 x 3 x 144
Multiply 144. What's the answer?
1 ft
3 ft
432 square inches
3 square feet is 432 square inches.
Chapter 12 Lesson 2
Perimeter and Area
Performance #1
How to change units with area.
2 yards
5 yards
How many square feet
are in a 5 x 2 rectangle?
2 yards
5 yards
90 square feet.
Multiply 10 x 9 = 90.
5 yards
5 yards
How many square feet
are in a 5 x 5 square?
5 yards
5 yards
175 square feet.
Multiply 25 x 9.
1 ft
5 ft
How many square inches
are in a 1 x 5 ft rectangle?
1 ft
5 ft
720 square inches
5 x 144 is 720 square inches.
1 yard
4 yards
How many square feet
are in a 1 x 4 rectangle?
1 yard
4 yards
36 square feet
4 x 9 = 36
2 ft
5 ft
How many square inches
are in a 2 x 5 ft rectangle?
2 ft
5 ft
1440 square inches
10 x 144 is 1440 square inches.
What sports field is like an acre?
1 acre is about
1 Football Field
That's without the end zones.
Chapter 12 Lesson 2
Perimeter and Area
Performance #2
How to change units with area.
4 yards
5 yards
How many square feet
are in a 5 x 4 rectangle?
4 yards
5 yards
180 square feet.
Multiply 20 x 9 = 180.
4 yards
4 yards
How many square feet
are in a 4 x 4 square?
4 yards
4 yards
144 square feet.
Multiply 16 x 9.
1 ft
4 ft
How many square inches
are in a 1 x 4 ft rectangle?
1 ft
4 ft
576 square inches
4 x 144 is 576 square inches.
2 yards
6 yards
How many square feet
are in a 2 x 6 rectangle?
2 yards
6 yards
108 square feet
12 x 9 = 108
3 yards
4 yards
How many square feet
are in a 3 x 4 yd rectangle?
3 yards
4 yards
108 square feet
12 x 9 = 108
What sports field is like an acre?
1 acre is about
1 Football Field
That's without the end zones.