Video Transcript
Calculate nine and three twelfths
minus two and eight twelfths. Give your answer as a mixed
number.
We’re trying to subtract a mixed
number from a mixed number. And in order to do that, there are
a few things we should think about. First of all, for the fraction
portions of our mixed number, do they have a common denominator? In this case, they do; both have a
denominator of 12. After that, we could convert both
of these mixed numbers into improper fractions. However, since our final answer
needs to be written in the form of a mixed number, there’s also another strategy we
could use.
We could try and subtract eight
twelfths from three twelfths, but we’ve run into a problem because eight twelfths is
larger than three twelfths. So, we’ll need to rewrite at least
the nine and three twelfths. One way to do that is to take one
away from our whole number nine and make that eight. And when we do that, we can add 12
to our numerator. This is because we’ve taken one
from our whole number, which is equal to twelve twelfths. And twelve twelfths plus three
twelfths equal fifteen twelfths. Eight and fifteen twelfths is equal
to nine and three twelfths. It’s just written in a different
format.
Then, we can say eight and fifteen
twelfths minus two and eight twelfths. In this case, we can subtract the
whole numbers and the mixed number pieces. To subtract eight twelfths from
fifteen twelfths, we say 15 minus eight equals seven. And the denominator stays the same,
12. And now, we work on the whole
number pieces. Eight minus two equals six. And that means nine and three
twelfths minus two and eight twelfths will equal six and seven twelfths. This is already in the form of a
mixed number. And seven twelfths cannot be
reduced any further, making six and seven twelfths our final answer.
