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## Number and quantity

# Rates | Worked example

## Video transcript

- [Instructor] We're
told, at Ceres's Grains, the price of couscous is $1.29 per pound and the price of quinoa
is $1.94 per pound. What is the price difference between 22 pounds of couscous
and 25 pounds of quinoa? So, why don't we pause this video, and see if you can work
through it on your own before we work through it together. Okay, now let's work through it together. So, the price difference
between 22 pounds of couscous and 25 pounds of quinoa. So, let's first think about
22 pounds of couscous. Couscous. How much is that going to cost? Well, its going to be 22 times the per pound price of couscous. You can do that as a unit rate of couscous or the unit price. So, 22 times $1.29, and we could use a calculator
to figure out that. I'll get the calculator out in a second. And then, if we wanted
to figure out the price of 25 pounds of quinoa. 25 pounds of quinoa. Well it's going to be 25
times the dollars per pound, and it is $1.94 per pound, so times $1.94. So we can get a calculator
out to figure these out. 22 times $1.29, so 22 pounds of couscous will be $28.38. $28.38, a little dollar sign here. And 25 pounds of quinoa and
multiply that times $1.94 is going to be $48.50. This is $48.50. So this is much larger, so what I'm going to do
to find the difference, because that's what they're asking, the price difference
between these two things. I'm going to do $48.50 minus $28.38. Now, some of you might already
be able to estimate that, because this is a
multiple choice question. You could say hey this is going to be a little bit more than $20, so you might immediately say hey, there's only one choice
that's right around there. But of course we can use a
calculator in the Praxis, and we can verify that. So, $48.50 minus 28 point
three eight, $28.38 is $20.12, which is exactly this
choice right over there.