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## Number and quantity

# Ratios and proportions | Worked example

## Video transcript

- [Instructor] We're told
that Ramon's restaurant, three enchiladas cost
the same as five tacos, and seven tacos cost the
same as three burritos. Which of the following cost the same? So pause this video and see
if you can figure this out, and you'd only pick one of these choices. All right, now let's do it together. And when you tackle a problem,
it's dealing with ratios, but my brain makes it, finds
it easier to work on this if we have some numbers attached to how much an enchilada costs
and how much a taco costs. So, let's see if we can
make these numbers work out. So, let's say that an enchilada costs $5. So I'm just making up that number here. So, enchilada, enchilada is $5. And so three enchiladas so
three times, I'll say E N C H is gonna be equal to $15. And then if that's the same as five tacos, I'm just looking at this
first part over here, three enchiladas cost
the same as five tacos, that if an enchilada cost $5,
three enchiladas cost $15, well then five tacos cost $15. So five times tacos is equal to $15. In which case, the tacos would be $3. So taco's would be equal to,
I'll just say tacos are $3. And then seven tacos would be
the same as three burritos. So seven times tacos, that's
gonna be equal to $21, that's gonna be the same
thing as three burritos. So three times, I'll just
say B U R for burritos, is equal to $21 and then
divide both sides by three, our burrito is gonna be $7 each. So our burrito is going to be $7. So on this tangible example
where an enchilada is $5, but I picked this to make
things more tangible, if enchiladas are $5 then tacos are $3 and burritos are $7. And so let's see which
of these make sense: So which of the following
would cost the same? Would three enchiladas cost
the same as three burritos? Well no, three enchiladas are $15 while three burritos as $21. So that's not gonna be the same. And you could have even ruled
that out before by saying look three enchiladas cost
the same as five tacos, you could write this in terms of tacos, and three burritos cost
the same as seven tacos. So that's another reason
why those two aren't gonna be the same. So four enchiladas and five burritos. So see four enchiladas are
gonna be $20, four times five, five burritos are gonna be $35. So we can rule that one out. Five enchiladas and seven burritos. Alright, five enchiladas, five times five, that's gonna be $25. Seven burritos are gonna be $49. Nope, we can rule that one out. Seven enchiladas and five burritos. This is interesting. Seven enchiladas times five, $35. Five burritos, five times seven, $35. This one looks good. Now let's see if we can just
rule this one out as well, nine enchiladas, that's gonna be $45, seven burritos are $49. And so these also are not equal.