# ADDING AND SUBTRACTING FRACTIONS. NS 2.1 Solve problems involving addition, subtraction, multiplication, and division of positive fractions and explain.

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NS 2.1 Solve problems involving addition, subtraction, multiplication, and division of positive fractions and explain why a particular operation was used for a given situation. Today’s objective: use our previous topic of equivalent fractions to help add and subtract fractions. Learning target: Answer at least 3 of the 4 fraction addition/subtraction problems correctly on the exit ticket.

Let’s use pizzas cut up into slices This pizza has been cut into 8 equal slices. A single slice is what fraction of the entire pizza? Each slice is ________ of the entire pizza.

At a party, there are a pepperoni pizza and a mushroom pizza. Both are cut into 8 equal slices. I eat 3 slices of pepperoni and 1 slice of cheese. Write an equation to calculate the total fraction of a pizza that I ate. =

But what do we do when the one pizza is cut into a different amount of slices than another pizza? Let’s say that again I eat 3 slices of pepperoni and 1 slice of cheese. Write a new equation to calculate the total fraction of a pizza that I ate. What can we do to make it easier to compare the amount eaten from each pizza? Cut the cheese pizza so it has the same number of slices as the pepperoni pizza.

Make the cheese pizza have 8 slices instead of 4: Now instead of, write it as When we cut the pizzas to have the same number of slices, the mathematical operation we did was finding a common denominator

How do we add and subtract fractions? If the fractions do not already have a common denominator, change them so that they do. Add or subtract the numerators like normal but keep the denominator the same.

Since you adding or subtracting pieces, the numerator changes. However, since all pieces will be the same size, the denominator remains the same. 5 8

Direct Station We will practice solving word problems which involve fractions.

Collaborative Station Use the spinners to create fractions. For example, if you spin a 3 and then a 4, the fraction would be ¾. For each problem, create two fractions, then add them. Write down the problem and the answer, including finding a common denominator if necessary.

Collaborative Station Example: Partner A spins a 1 and a 2, creating ½. Partner B spins a 5 and a 3, creating Both partners write down They find the LCM is 6, so they rewrite their problem as They solve their equation to get the answer

Independent Station We are switching to ST Math’s unit on adding and subtracting fractions. Write down your calculations on your paper.