Lesson 4 Another Look at the Standard Algorithm

- Let’s subtract from numbers with zeros.

Warm-up Number Talk: Differences

Find the value of each difference mentally.

$87 - 24$
$387 - 124$
$6, 387 - 129$
$6, 387 - 4, 329$

Activity 1 Lots of Zeros

Problem 1

Find the value of each difference.

Problem 2

Find the number that makes each expression true.

Activity 2 Ways of Finding Differences

To find the value of $20, 000 - 472$ , Priya and Han set up their calculations differently.

subtraction algorithm 20,000-472 — Priya

Han

Use both methods to find the difference of 20,000 and 472.
Kiran uses another method. Explain how Kiran found the value of $20, 000 - 472$ .

$\begin{aligned} 472 + 8 & = 480 \\ 480 + 20 & = 500 \\ 500 + 500 & = 1, 000 \\ 1, 000 + 19, 000 & = 20, 000 \end{aligned}$

$19, 000 + 500 + 20 + 8 = 19, 528$
Which method do you prefer? Or do you prefer another way? Explain your reasoning.
Find the value of $50, 400 - 1, 389$ . Show your reasoning.