We included HMH Into Math Grade 3 Answer Key PDF Module 9 Lesson 2 Use Mental Math Strategies for Addition and Subtraction to make students experts in learning maths.
HMH Into Math Grade 3 Module 9 Lesson 2 Answer Key Use Mental Math Strategies for Addition and Subtraction
I Can use mental math strategies to add and subtract with 2- and 3-digit numbers.
Spark Your Learning
Scientists travel to Yellowstone National Park to study different parts of the park. They drive 203 miles the first day and 437 miles the second day. How many miles do the scientists drive?
Answer:
640
Explanation:
On the first day, they drove 203 miles, and on the second day 437 miles.
The total number of miles the scientists drove is 203 + 437 = 640 miles.
Show how you can use mental math to find the total number of miles. Use words and equations.
Turn and Talk Write an equation using 2- or 3-digit numbers that you think are easy to add or subtract using mental math. Why did you choose those numbers?
Build Understanding
1. Scientists take photos in different parts of Yellowstone National Park to study bison migration patterns. How many photos do the scientists take in Pelican Valley and Gibbon Valley?
Answer:
590
Explanation:
The number of photos does the scientists take in Pelican Valley and Gibbon Valley is 233 + 357 = 590.
Draw jumps and label the number line to show your thinking.
2. How many more photos do the scientists take in Gibbon Valley than in Hayden Valley?
Draw jumps and label the number line to show your thinking.
Turn and Talk Compare your number line strategy with a classmate. How can you use the number line to show a different way to add or subtract?
Step It Out
3. Use friendly numbers to add mentally.
Add 317 + 45.
Answer:
362
Explanation:
Let us solve the given question
317 + 3 + 42
320 + 42
362.
A. Make 317 a friendly number by adding 3.
317 + 3 = ___
Answer:
320
Explanation:
Let us solve the given question
317 + 3
320.
B. Use the friendly number to add. __ + 45 = ___
Answer:
217 + 45 = 262
Explanation:
Let us slove the given question
217 + 3 + 42
220 + 42
262
C. Adjust the sum by subtracting 3. ___ – 3 = ___
Answer:
6 – 3 = 3
Explanation:
Let us solve the given question
6 – 3 = 3
3
D. What is 317 + 45? ____
Answer:
362
Explanation:
Let us solve the given question
Add the given numbers
317 + 45
362
4. Use friendly numbers to subtract mentally.
Subtract 275 — 149.
Answer:
126
Explanation:
subtract the given numbers
275 – 149
126
A. Make 149 a friendly number by adding 1. 149 + 1 = ___
answer:
150
Explanation:
Let us solve the given question
140 + 9 + 1
150
B. Use the friendly number to subtract. 275 – __ = ____
Answer:
275
Explanation:
The user-friendly number to subtract is 275.
C. Adjust the difference by adding 1. ___ + 1 = ___
Answer:
1 + 1 = 2
Explanation:
The difference by adding 1 is 2.
D. What is 275 – 149? _______
Answer:
126
Explanation:
The difference between the two numbers is 126.
Turn and Talk What mental math strategy would you use to add 352 + 234? Explain your thinking.
Answer:
586
Explanation:
Let us solve the problem
350 + 2 + 230 + 4
580 + 6
586
Check Understanding Math Board
Question 1.
Eli’s family drives 112 miles on Sunday and 248 miles on Monday. How many miles do they drive? ____
Answer:
360
Explanation:
Eli’s family drives 112 miles on Sunday and 248 miles on Monday.
Eli’s family drove a total of 360 miles on both Sunday and Monday.
Use mental math to find the sum or difference.
Question 2.
384 + 22 = ___
Answer:
406
Explanation:
The sum of the given number is 406.
Question 3.
79 – 36 = ___
Answer:
43
Explanation:
The difference between the given numbers is 43.
On Your Own
Question 4.
Use Tools Trent travels to Washington, D.C. for a business trip. He flies 454 miles, changes planes, and then flies 326 more miles. How many miles does Trent fly? Explain how you can use a number line to solve.
Answer:
780.
Explanation:
Trent travelled 454 + 326 = 780 miles for a business trip.
Use mental math to find the sum or difference.
Question 5.
46 + 24 = ___
Answer:
70
Explanation:
The sum of the two numbers is 70.
Question 6.
639 – 425 = ___
Answer:
214.
Explanation:
The difference between the two given numbers is 214.
Question 7.
953 – 836 = ____
Answer:
117.
Explanation:
The difference between the two given numbers is 117.
Question 8.
499 – 121 = ___
Answer:
378
Explanation:
The difference between the two given numbers is 378.
Question 9.
148 – 36 = ____
Answer:
112.
Explanation:
The difference between the two given numbers is 378.
Question 10.
349 + 263 = ___
Answer:
612.
Explanation:
The sum of the given two numbers is 612.
Question 11.
Explain how you can use friendly numbers to find 574- 397.
______________________
______________________
Answer:
177
Explanation:
The user-friendly number to find the number is 177.
Question 12.
Open Ended Write a word problem for 126 + 150. Then use mental math to solve.
Answer:
276
Explanation:
Let us solve the given problem
126 + 150
100 + 20 + 6 + 100 + 50
100 + 100 + 50 + 20 + 6
200 + 70 + 6
270 + 6
276
I’m in a Learning Mindset
What mental math strategies work best for me?
_______________________
_______________________
Answer:
The mental math strategies that work best for me are by solving multiple digit sums from right to left, starting with the ones, and borrowing/regrouping as per the given question.
Let’s take 44 + 27 as an example:
First, we add the 4 and 2 in the tens column, giving us 60.
Now we add the 4 and 7 in the one’s column, giving us 11.
Add the 60 to the 11, and we get a total of 71.