Adding different units for weight

We have 11 ounces plus 29 ounces
plus 5 pounds is equal to how many pounds,
or blank pounds? So we need to add these three
quantities right here, and they want us to give the
answer in pounds. And we can only add quantities
that have the same units. So let’s just add these ounces
first, just to get them out of the way. And then we could see, maybe we
can convert them to pounds, or convert the pounds
to ounces. We’ll probably convert them to
pounds, so that our final answer is in pounds. So if we just add 11
ounces plus 29 ounces, what do we get? Well, 11 plus 29 is 40. Let me write it like this. This right here is 40 ounces. So we need to add 40 ounces to
5 pounds to get a certain number of pounds. So let’s convert this right here
to pounds, and then, once we have that in pounds, we can
just add it to that, and then we’ll have our final answer. So 40 ounces, we want to
convert it to pounds. So we need to multiply it by
something where, in the units, we have ounces in the
denominator, and we have pounds in the numerator. And we need that so that these
ounces cancel out with these ounces, and we’re just
left with pounds. And we know already that there
are 16 ounces per pound. So there are 16 ounces
per 1 pound. Or you could say there’s 1 pound
per every 16 ounces. Or you could say there’s 1/16
of a pound per ounce. Either way, if you multiply
these two quantities, the ounces cancel out. And this whole quantity becomes,
when you multiply it out, you’re left with
40 divided by 16. 40/16. It’s really 40 times 1
over 16, but the 1 doesn’t change anything. And then 40/16 pounds. And let’s see if we can write
this as a mixed number, or if we can simplify this
a little bit. Both of these numbers
are divisible by 8. So let’s divide them
both by 8. If you divide 40 by
8, you get 5. You divide 16 by 8, you get 2. So it’s 5/2. If we want to write this as a
mixed number– or even better, let’s write it as a decimal. This is 5 divided by 2. 2 goes into 5 2 times. 2 times 2 is 4. Subtract. You have a remainder, 1. We want a decimal, so let’s put
the decimal right there and keep bringing down 0’s. So let’s bring down
a 0 right there. 2 goes into 10 5 times. 5 times 2 is 10. And we have no remainder. So this is exactly 2.5,
which makes sense. 5 over 2 is the same thing as
2 and 1/2 as a mixed number, which is the exact same
thing as 2.5. This first part right here
simplified down to 5/2 pounds, or 2.5 pounds. So the problem becomes 2.5
pounds plus 5 pounds. And 2.5 plus 5, fairly
straightforward, it’s 7.5. So this is equal
to 7.5 pounds. 7.5 pounds is our answer,
and we’re done.

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