Welcome to math magic with Mrs. Fredette. So today we're talking about benchmark fractions. So what is a benchmark fraction?
Well, it's a number that we use a lot. You've probably already heard of a lot of these like 1/2
1/3 1/4 1/10 things like that. We see them all the time in the world around us. So we're gonna
define what those benchmark fractions are and then we're gonna plot them on a number line so we can compare them and really see
which ones are bigger which ones are smaller. That way we know
how to compare them later when we do other projects other real world kind of things.
I'm gonna explain all that to you show you how to do it here on a number line and then I'm gonna give you
A chance to do it as well in your math journals. Ready? Here we go!
All right, we are going to
plot some benchmark fractions on our number line
So I'm gonna walk through this and then you're gonna do it. You can do it along with me or you can watch and then
do it after I've completed it. But at the end of this when you walk away, you need to have a
number line with benchmark fractions marked on it in your math journal. Ready to go?
Alright, we need a straightedge and we need some colored pencils.
First thing I want to do is make my number line - just drawing right along my straightedge.
For this we only need to go from 0
on
the left side
to 1 on the right side.
All right. First color I'm going to use you can use whatever colors you like, but use a different color for each benchmark fraction.
First one we're gonna do is 1/2.
So that looks like this 1 over 2,
Which means we need to divide the number line into two pieces. So right here in about the middle
I'm gonna put my mark and I'm gonna label this
one
There we go
The next one we're gonna do is one third. I'm gonna pick up a new color and I'm gonna write 1/3
This means that we have to divide our number line into three pieces
three equal pieces as equal as we can make them so I'm gonna go about here and
The other one would be about here and I'm only gonna label this first one. This is
1/3
Next one we're gonna do is
1/4 so let's write that up here 1 over 4
Which means I need my number line divided into 4 pieces
Well, I've already got one that's divided in 2 so I can use that I'm going to take that and then divide each of those
two sections into just 2 pieces
so if I come here and I look to about the middle that's gonna be about right here and that's
1/4 I can do it on the other side, but we're not
labeling anything over there
Right at this moment. There's one for
All right, 1/5 next one up is 1/5. So I've got my orange. I'm gonna put it up at the top
1/5 now 1/5 that means I've got to divide my number line into five
Five equal pieces, okay
So I can't
Really use any of my existing marks directly
But I know that if I'm gonna divide this into five those pieces are gonna be just a little bit smaller
Right just a little bit smaller if you had a pizza and you had to divide that Pizza among five people
Those slices would be a little bit smaller than if you just had to divide it over four people
Or you can think about a dollar, right?
If I divide a dollar into four parts, that's 25 cents each right 1/4 if I divide that same dollar
Into 5 parts, that means they're about 20 cents each, right?
So just a little bit a little bit smaller than the 1/4 I'm gonna put it right here. And again, we're not
Terribly concerned with where those marks down the line. So we're just gonna label this one fit and move on to our next one
All right, the next one we're gonna do I'm picking up another color. This color is gonna be purple. We are gonna do one-eighth
One-eighth. So one ace that's kind of got a relationship with 1/4 if I divide my
1/4 space in half
that will give me 2 spaces there, right and
Then that would give me 8 spaces across the whole thing because if I had 4 spaces
and each of those 4 spaces I divide into two spaces more each 4 times 2 is 8 so
That will work
so I'm just gonna look at this space right here and I'm gonna come about halfway and I'm gonna make my mark 1/8
There we go a
Couple left to go next one we're gonna do is 1/10
1/10 with my red pencil
So 1/10 is about is half of 1/5, right because 5 times 2 is 10
so if I take my 1/5 segment and I divide that into
I'm gonna get a segment that is about 1/10 of my number line
Great job laughs one we're gonna do is
1/100 1/100 this is very very tiny. Very very small. That's right at the top 1 over 100
This means we would take this number line and divide it into
100 equal pieces or like a dollar right? A dollar is 100 cents 100 pennies same thing
I would take this space from zero to
1/10 though for our purposes and I would think okay if I divide that into 10 pieces
That would give me my tents, right?
so
1 2 3 4 5 6 7 8 9 10 right and there is my
1/100 so there's your number line. I want to see from each of you a number line in your math journal that has these
7
benchmark fractions labeled
Have fun
You
