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In these examples we're asked to add fractions that have the same denominator
both a and b
each set of fractions have the scene denominator
we can look at the first fraction here five twelfths
as five copies of one twelfth
and the second fraction as two copies of one twelfth
that would give s
total of seven copies
of one twelfth which is seven
twelfths so you can look at
fraction addition more formally as
saying
well you have to have a common denominator to add two fractions and then
you add the numerators
but this idea of copies of
one over the denominator might help you remember when you need a common
denominator
and when you don't
if you look at the second one
three eighths plus seven-eighths that's three copies of one-eighth plus seven
copies of one-eighth is ten copies of one eighth or ten eighths
we're gonna need to reduce that using
the method of finding common factors
so I'm going to write the numerator
as two times five
denominator as two times four
and then remove
the comment factor
two
leaving me with
five over four
i'm also going to write that as a mixed number
four goes into five one time
with one
fourth left over
so these are the final results here and
you'll need to read there is nothing here that really tells us to
choose between a mixed number or improper fractions so I'm going to leave both
of these you'll need to read the directions in whenever problem that you're working
with and see what form is required