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Videos to help Grade 5 students learn how to convert numerical expressions into unit form as a mental strategy for multi-digit multiplication.

Common Core Standards: 5.OA.1, 5.OA.2, 5.NBT.5

Related Topics:
Lesson Plans and Worksheets for Grade 5

Lesson Plans and Worksheets for all Grades

More Lessons for Grade 5

Common Core For Grade 5

New York State Common Core Math Module 2, Grade 5, Lesson 4

Lesson 4 Concept Development

Problems 1–2
8 × 31
8 × 29

Problems 3–4
49 × 20
20 × 51

Problems 5–6
101 × 12
12 × 98





Lesson 4 Problem Set

1. Circle each expression that is not equivalent to the expression in bold.
a. 16 × 29
29 sixteens
16 × (30 – 1)
(15 – 1) × 29
(10 × 29) – (6 × 29)

b. 38 × 45
(38 + 40) × (38 + 5)
(38 × 40) + (38 × 5)
45 × (40 + 2)
45 thirty-eights

2. Solve using mental math. Draw a tape diagram and fill in the blanks to show your thinking.
c. 79 × 14 = _____ fourteens
Think: ____ fourteens – 1 fourteen
= (____ × 14) – (___ × 14)
= ______ - ______ = ______.

d. 21 × 75 = ____ seventy-fives
Think: ___ seventy-fives + ___ seventy-five
= (___ × 75) + (___ × 75)
= ______ + ______ = _____

3. Define the unit in word form and complete the sequence of problems as was done in Problems 3–4 in the lesson.
a. 19 × 15 = 19 __________
Think: 20 _______ – 1 __________
= (20 × ____) – (1 × ___)
= _______ – _______ = _______

b. 14 × 15 = 14 ________
Think: 10 _________ + 4 _________
= (10 × ____) + (4 × _____)
= _______ + _______ = _______



 

Lesson 4 Homework

1. Circle each expression that is not equivalent to the expression in bold.
a. 37 × 19
37 nineteens
(30 × 19) – (7 × 29)
37 × (20 – 1)
(40 – 2) × 19

2. Solve using mental math. Draw a tape diagram and fill in the blanks to show your thinking.
b. 11 × 26 = ________ twenty-sixes

Think: _______ twenty-sixes + ____ twenty-sixes
= (_____ × 26) + (_____ × 26)
= __________ + __________ = _________

3. Define the unit in word form and complete the sequence of problems.
c. 19 × 11 = 19 ____________________

Think: 20 ________ – 1 ________
= (20 × ______) – (1 × _____)
= __________ – __________ = __________





This video demonstrates how to use mental math to evaluate expressions involving multiplication.

3. Define the unit in word form and complete the sequence of problems.

a. 29 × 12 = 29 ____________________

Think: 30 _____________ – 1 _____________
= 30 × ______) – (1 × _____)
= __________ – __________ = __________

6. Joy is helping her father to build a deck that measures 14 ft by 19 ft. Find the area of the deck using a mental strategy. Explain your thinking.



 

Rotate to landscape screen format on a mobile phone or small tablet to use the Mathway widget, a free math problem solver that answers your questions with step-by-step explanations.


You can use the free Mathway widget below to practice Algebra or other math topics. Try the given examples, or type in your own problem and check your answer with the step-by-step explanations.


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