 # Multiply and Divide with Familiar Facts

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Lesson Plans and Worksheets for Grade 3
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Examples, solution, and videos to help Grade 3 students learn how to multiply and divide with familiar facts using a letter to represent the unknown.

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

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

Application Problem

Twenty-four people line up to use the canoes at the park. Three people are assigned to each canoe.
How many canoes are used?

Note: Students may choose to model either as division or as multiplication. In the Concept Development this problem provides a context for using a letter to represent the unknown.

Concept Development

For this problem, we might choose letter c to help us express that the unknown stands for how many canoes are used in the problem.

How will using a letter to express the unknown value change the way we model and solve?

Problem 1: Use a letter to represent the unknown in multiplication.
Problem 2: Use a letter to represent the unknown in division.

Example:
Twenty-one students are grouped in threes to go on a field trip. How many groups of students are there?.

Lesson 3 Homework

1. a. Complete the pattern.
b. Find the value of the unknown.
10 × 2 = d
d = 20
10 × 6 = w
w =_____
3 × 10 = e
e =_____
10 × 7 = n
n =_____
f = 4 × 10
f =_____
g = 8 × 10
g =_____
p = 5 × 10
p =_____

2. Each equation contains a letter representing the unknown. Find the value of the unknown. Lesson 3 Homework

3. Pedro buys 4 books at the fair for \$7 each.
a. What is the total amount Pedro spends on 4 books? Use the letter b to represent the total amount Pedro spends, and then solve the problem.
b. Pedro hands the cashier 3 ten dollar bills. How much change will he receive? Write an equation to solve. Use the letter c to represent the unknown.

4. On field day, the first grade dash is 25 meters long. The third grade dash is twice the distance of the first grade dash. How long is the third grade dash? Use a letter to represent the unknown and solve.

Try the free Mathway calculator and problem solver below to practice various math topics. Try the given examples, or type in your own problem and check your answer with the step-by-step explanations.  