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Adding & Subtracting Fractions Song
In a future time, when AI robots have taken over running pizzerias on a planet orbiting Alpha Centauri, the robot Zigon takes orders and then adds and subtracts fractions before the Pizzamatic-5000 serves up large pepperoni and cheese pizzas for its alien visitors! Adding Fractions has never been so stellar or astral.
This is how the least common multiple’s found:
write a list of each denominator’s multiples down;
the smallest number you can find in both of them
is the least common multiple (a.k.a. the LCM.)
The least common multiple can also be
called the least common denominator - or LCD.
It stays the same in the difference or the sum
when you subtract or add two fractions.
Three-sixths of a pizza minus one-fourth:
find the LCM, which is twelve, of course.
(Twelve is the least common denominator.)
Make equivalent fractions (six-twelfths and three-twelfths).
Then, do the subtraction: six minus three is three...
three-twelfths of a pizza at the pizzeria.
Find the least common multiple; that’s the first action.
Next, is finding equivalent fractions.
Then, do the addition or subtraction.
Simplify like an automatic reaction.
Two-fourths of a pizza plus one-fifth:
it smelled so good we had to give it a sniff.
The LCM was twenty (the new denominator).
We found equivalents quickly: ten-twentieths plus four-twentieths... fourteen-twentieths of a pizza at the pizzeria.
Five-sixths of a pizza minus one-third:
I knew the LCM was six, and have you heard?
It’s also called the least common denominator.
I found equivalent fractions (five-sixths and two-sixths).
Then, I did the subtraction: five minus two is three...
three-sixths of a pizza at the pizzeria.
If you are interested in getting ideas on how to plan a robust standards-aligned telling time lesson, we recommend checking out Instructure's recommendations for common core standards 4.NF.4, and 5.NF.1 . These pages help break down standard language, lay out the grade-appropriate level of rigor for each concept, and offer a variety of suggestions for activities (lesson seeds) that help students achieve their learning targets