# Interpret Unknown - Multiplication and Division

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Examples, videos, and solutions to help Grade 3 students learn how to interpret the unknown in multiplication and division to model and solve problems.

Common Core Standards: 3.OA.3, 3.OA.4, 3.OA.5, 3.OA.7, 3.OA.9, 3.OA.1, 3.OA.2, 3.OA.6

### New York State Common Core Math Grade 3, Module 3, Lesson 15

Concept Development

Problem 1: Interpret the unknown in multiplication.

Ada buys 9 packs of highlighters with 4 in each pack. After giving 1 highlighter to each classmate, she has 17 left. How many highlighters did Ada give away?

Problem 2: Interpret the unknown in division.

Write the following problem: Eliza finds a bag of 72 marbles and runs to share them with 8 of her friends. She’s so excited that she drops the bag and loses 18 marbles. How many marbles will Eliza and each of her friends get?

Lesson 15 Problem Set Sample Solution

5. Cara bought 9 packs of beads. There are 10 beads in each pack. She always uses 30 beads to make each necklace. How many necklaces can she make if she uses all the beads?

Lesson 15 Homework

1. The store clerk equally divides 36 apples between 9 baskets. Draw a tape diagram and label the number of apples in each basket as a. Write an equation and solve for a.

2. Elijah gives each of his friends a pack of 9 almonds. He gives away a total of 45 almonds. How many packs of almonds did he give away? Model using a letter to represent the unknown, then solve.

3. Denice buys 7 movies. Each movie costs \$9. What is the total cost of 7 movies? Use a letter to represent the unknown. Solve.

4. Mr. Doyle shares 1 roll of bulletin board paper equally with 8 teachers. The total length of the roll is 72 meters. How much bulletin board paper does each teacher get?

5. There are 9 pens in a pack. Ms. Ochoa buys 9 packs. After giving her students some pens, she has 27 pens left. How many pens did she give away?

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