Lesson 12 Subtract Strategically

- Let’s consider when to use algorithms and when to use other strategies to subtract.

Warm-up Number Talk: Threes

Find the value of each expression mentally.

$2 \times 6$
$3 \times 6$
$2 \times 7$
$3 \times 7$

Activity 1 How Would You Subtract?

Use a strategy or algorithm of your choice to find the value of each difference. Show your reasoning. Organize it so it can be followed by others.

$451 - 329$
$382 - 190$
$924 - 285$
$600 - 478$
$505 - 417$

Activity 2 Greatest Difference, Smallest Difference

Decide with your partner whether you will try to make the greatest difference or smallest difference.
Take turns spinning and recording a digit in the hundreds, tens, or ones place. Continue until your numbers are complete.
Find the difference.
Compare your values.
Write a comparison using >, <, or =.
Play again.

Practice Problem

Problem 1

Use a strategy or algorithm of your choice to find the value of each difference.

$573 - 299$
$653 - 341$
$371 - 158$