### Video Transcript

The following is a recipe for 20
crepes: three eggs, 250 grams of flour, 500 millilitres of milk. Rob has 12 eggs, one kilogram of
flour, and 1.5 litres of milk. What is the maximum number of
crepes he can make?

To answer this question, we’ll need
to work out how many batches of the recipe, that’s how many batches of 20 crepes
that Rob can make with each individual ingredient. Let’s begin with the eggs. Rob has 12 eggs and the recipe call
for three eggs. We can, therefore, work out the
number of batches that Rob can make with these eggs by dividing 12 by three. That’s four. So he can make four batches of 20
with his eggs.

Let’s repeat this with the
flour. He has one kilogram of flour and
each recipe calls for 250 grams. We can only repeat that process
from before if the units are the same. So we remind ourselves that each
one kilogram of flour is the same as 1000 grams. And we divide 1000 by 250 since
that’s the amount of flour required for a batch of pancakes. 1000 divided by 250 is four. So he can make four batches of
pancakes with his flour.

Now this might have been a sum you
could do in your head. However, if not, remember that we
can write division as a fraction. 1000 divided by 250 can be written
as 1000 over 250. We then simplify as far as
possible. First, we can divide both the
numerator and the denominator by 10. And 1000 over 250 is the same as
100 over 25. At this point, you might be able to
do that in your head. If not, we can divide both 25 and
100 by five. That gives us 20 over five or 20
divided by five, which we of course know is four. So that’s another way of working
out 1000 divided by 250.

Finally, let’s work out how many
batches Rob can make with his milk. One litre is equivalent to 1000
millilitres. We can work out how many
millilitres there are in 1.5 litres then by multiplying by 1000. When we multiply by 1000, we move
the digits to the left three places. So 1.5 multiplied by 1000 is 1500
millilitres. Each batch requires 500 millilitres
of milk. So we’re going to divide 1500 by
500.

We could again use the fraction
method. But we recall that 15 divided by
five is three. So that means that 15 hundred or
1500 divided by 500 is three. So he can make three batches of
pancakes with his milk. This means the most pancakes he can
make is three batches. He has enough flour and eggs for
more. But he doesn’t have enough
milk.

Each batch makes 20 pancakes. So he can make three times this
amount. Three multiplied by 20 is 60. So he can make 60 pancakes or 60
crepes with his ingredients.