Adding decimals: science experiment | 4th grade math (TX TEKS) | Khan Academy

- [Instructor] We're told, "Mia is doing

a science experiment.

She pours 0.9 liter of
vinegar into a container.

Then, she adds 0.3 of a liter
of oil to the container.

How much total liquid
is in Mia's container?"

Pause this video and
try to figure that out.

All right, so what we really want to do

is we want to add 0.9
liters to 0.3 liters.

So let's just do that.

So we are going to have 0.9,

and I could put the units there if I like,

and I'm going to add that to 0.3.

Now when I'm going to add
things, I want to make sure

that my decimals are lined up

so I can add the same
places to the same places.

So let's get started.

So we can go to the tenths place.

I have 0.9 plus 0.3.

That's 12 tenths.

Now I can't write 12
tenths in the tenths place,

but I could write that 12
tenths is the same thing

as 0.2 and a whole.

Or another way to think about it,

it's the same thing as 1.2,
if you have 0.9 plus 0.3.

Or another way, sometimes
people would say, "Write the 2.

Carry the 1. Regroup the 1."

But the reason why you're doing that,

this is 12 tenths, and 12
tenths is the same thing

as 0.2 and a whole.

And then I have 1 whole
and no other wholes,

so it's just going to be
1 whole right over there,

and then my decimals right
over there, and I am done.