Subtracting a fraction from a whole number

- [Instructor] Let's say
we wanted to figure out

what six minus 3/4 is equal to.

Pause this video and work
through this on your own

before we work through this together.

All right, now there's a couple of ways

that we could think about this.

The first way is we could
represent this six wholes

as a bunch of fourths.

So how many fourths is six wholes?

Well, we already know
that one is equal to 4/4.

So six wholes, that's
gonna be six times as many.

So instead of 4/4, you're
going to have 24/4.

So, 24/4 is the same as six.

And you could see that

because you're going
to use 4/4 for a whole.

And you could do that six times.

And now, we can subtract
the 3/4 from that.

And what does that get us?

Well, if I have 24 of something
minus three of something,

that's going to be 21 of that something.

So, 24/4 minus 3/4 is 21/4.

Now, there's another way that
you could think about this.

You could say,

well, six is the same
thing as five plus one.

And you might say, why would I do that?

Well, if you have one here,

you could subtract 3/4 from that.

So you could subtract three,

lemme do that in a different color.

You could subtract the
3/4 now from the one.

And so this is going to
be equal to five plus,

and let's rewrite one over here.

Lemme just do it in a different color.

I'm having trouble changing colors today.

One is how many fourths?

Well, we already wrote it over here.

It's 4/4.

So that's 4/4 minus 3/4.

And what is that going to be equal to?

Well, that's going to
be equal to, once again,

we have this five over here plus

4/4 minus 3/4 is, of course,
this is going to be one.

This over here is going to be 1/4.

So you get five plus 1/4

is going to be equal to five and 1/4.

You might say, hey, is that
the same thing as 21/4?

Well, yes it is because five is what?

That's the same thing as 20/4.

So it says 20/4 plus 1/4, which is 21/4.

Another way you could think about this,

if you were to take four,
it goes into 21 five times

with a remainder of one.

So there's many different ways
that you could approach this.