# McGraw Hill My Math Grade 3 Chapter 2 Lesson 7 Answer Key Add Three-Digit Numbers

All the solutions provided in McGraw Hill Math Grade 3 Answer Key PDF Chapter 2 Lesson 7 Add Three-Digit Numbers will give you a clear idea of the concepts.

## McGraw-Hill My Math Grade 3 Answer Key Chapter 2 Lesson 7 Add Three-Digit Numbers

When you add, you may need to regroup. To regroup means to rename a number using place value.

Math in My World

Example 1
During a weekend trip to Vermont, the Wildlife Club saw 127 wrens and 58 eagles. How many wrens and eagles did the Wildlife Club see?

Find 127 + 58.

Check for Reasonableness
185 is close to the estimate of 190. It makes sense. The answer is reasonable.
127 + 58 = 185
So, the Wildlife Club saw 185 wrens and eagles.

You can write a number sentence to find the unknown, or missing number.

Example 2
One box of butterfly nets costs SI75. Another box costs $225. How much do the boxes of nets cost altogether? Write a number sentence to find the unknown. 2. Add the tens and hundreds. 1 ten + 7 tens + 2 tens = 10 tens Regroup 10 tens as 1 hundred and 0 tens. 1 hundred + 1 hundred + 2 hundreds = 4 hundreds Check for Accuracy Use the Commutative Property to check your answer. No matter in which order you add, the sum is the same. So,$175 + $225 =$400. The unknown is $400. The net cost$400.

Talk Math
Why is it important to check for reasonableness?
Answer:
Checking for reasonableness is a process by which students evaluate estimations to see if they are reasonable guesses for a problem.
To be reasonable means to be as much as is appropriate or fair.
In math, reasonableness can be defined as checking to verify that the result of the solution or the calculation of the problem is correct or not, be either estimating or by plugging in your result to check it.

Guided Practice

Add.

Question 1.

Answer:

Explanation:
1. Add the ones
4 ones + 7 ones = 11 ones.
regroup 11 ones as 1 ten and 1 one
2. Add the tens and hundreds.
1 ten + 6 ten + 1 ten = 8 ten
1 hundred + 0 hundred = 1 hundred
So 164 + 17 = 181

Question 2.

Answer:

Explanation:
1. Add the ones
6 ones + 9 ones = 15 ones.
regroup 15 ones as 1 ten and 5 one
2. Add the tens and hundreds.
1 ten + 5 ten + 2 ten = 8 ten
1 hundred + 2 hundred = 3 hundred
So 156+ 229= 385

Independent Practice

Add. Check for reasonableness.

Question 3.

Estimate:
780
Answer:

Explanation:
1. Add the ones
9 ones + 9 ones = 18 ones.
regroup 18 ones as 1 ten and 8 one
2. Add the tens and hundreds.
1 ten + 5 ten + 1 ten = 7 ten
7 hundred + 0 hundred = 7 hundred
So 759+ 19= 778
778 is close to estimate of 780

Question 4.

Estimate:
470
Answer:

Explanation:
1. Add the ones
5 ones + 6 ones = 11 ones.
regroup 18 ones as 1 ten and 1 one
2. Add the tens and hundreds.
1 ten + 4 ten + 2 ten = 7 ten
4 hundred + 0 hundred = 4 hundred
So 445+ 26= 471
471 is close to estimate of 475

Question 5.

Estimate: 440
Answer:

Explanation:
1. Add the ones
5 ones + 3 ones = 8 ones.
2. Add the tens and hundreds.
4 ten + 9 ten = 13 ten
regroup 13 ten as 1 hundred and 3 ten
1 hundred + 3 hundred = 4 hundred
So $345+$93= $438 438 is close to estimate of 440 Question 6. Estimate: 640 Answer: Explanation: 1. Add the ones 7 ones + 7 ones = 14 ones. regroup 14 ones as 1 ten and 4 one 2. Add the tens and hundreds. 1 ten + 2 ten + 1 ten = 4 ten 4 hundred + 2 hundred = 6 hundred So$427+ $217=$644
644 is close to estimate of 650

Question 7.

Estimate:
650
Answer:

Explanation:
1. Add the ones
7 ones + 1 ones = 8 ones.
2. Add the tens and hundreds.
9 ten + 5 ten  = 14 ten
regroup 14 tens as 1 hundred and 4 ten
1 hundred + 5 hundred = 6 hundred
So 597+ 51= 648
648 is close to estimate of 651

Question 8.

Estimate:
300
Answer:

Explanation:
1. Add the ones
9 ones + 9 ones = 18 ones.
regroup 18 ones as 1 ten and 8 ones
2. Add the tens and hundreds.
7 ten + 1 ten + 1 ten  = 9 ten
2 hundred + 0 hundred = 2 hundred
So 279+ 19= 298
298 is close to estimate of 300

Add. Use the Commutative Property of Addition to check for accuracy.

Question 9.

Answer:

Explanation:
No matter in which order you add, the sum is the same.

Question 10.

Answer:

Explanation:
No matter in which order you add, the sum is the same.

Algebra Add to find the unknown.

Question 11.

The unknown is ____.
Answer:

Explanation:
1. Add the ones
3 ones + 7 ones = 10 ones.
regroup 10 ones as 1 ten and 0 one
2. Add the tens and hundreds.
1 ten + 4 ten + 1 ten = 6 ten
2 hundred + 0 hundred = 2 hundred
So 43+ 217= 260
The unknown is 260

Question 12.

The unknown is ____.
Answer:

Explanation:
1. Add the ones
7 ones + 7 ones = 14 ones.
regroup 14 ones as 1 ten and 4 one
2. Add the tens and hundreds.
1 ten + 0 ten + 2 ten = 3 ten
6 hundred + 0 hundred = 6 hundred
So 607+ 27= 634
The unknown is 634

Question 13.

The unknown is ____.
Answer:

Explanation:
1. Add the ones
3 ones + 1 ones = 4 ones.
2. Add the tens and hundreds.
7 ten + 9 ten  = 16 ten
regroup 16 tens as 1 hundred and 6 ten
1 hundred + 1 hundred + 5 hundred= 7 hundred
So 173+ 591= 764
The unknown is 764

Problem Solving

Write a number sentence with a symbol for the unknown. Then solve.

Question 14.
A 10-speed bike is on sale for Si 99, and a 12-speed racing bike is on sale for $458. How much do the two bikes cost altogether? Answer: two bikes cost altogether 557 Explanation: 10-speed bike is on sale for Si 99 12-speed racing bike is on sale for$458
Si 99 + $458 = 557 Question 15. Mathematical PRACTICE 2 Use Algebra A newspaper surveyed 475 students about their favorite sport. A magazine surveyed 189 students about their favorite snack. How many students were surveyed by the magazine and newspaper? Answer: students surveyed by the magazine and newspaper are 664 Explanation: newspaper surveyed 475 students A magazine surveyed 189 students Total 475 + 189 = 664 HOT Problems Question 16. Mathematical PRACTICE 2 Use Number Sense Use the digits 3, 5, and 7 to make two three-digit numbers with the greatest possible sum. Use each digit one time in each number. Write a number sentence. Answer: The two three digit numbers are 735 and 537 735 + 537 = 1272 Question 17. Building on the Essential Question How can I use place value to add three-digit numbers? Answer: For example add 123 + 123 = 246 Explanation: 1. Add the ones 3 ones + 3 ones = 6 ones. 2. Add the tens and hundreds. 2 ten + 2 ten = 4 ten 1 hundred + 1 hundred = 2 hundred So 123+ 123= 246 ### McGraw Hill My Math Grade 3 Chapter 2 Lesson 7 My Homework Answer Key Practice Add. Check for reasonableness. Question 1. Estimate: 280 Answer: Explanation: 1. Add the ones 8 ones + 9 ones = 17 ones. regroup 17 ones as 1 ten and 7 one 2. Add the tens and hundreds. 1 ten + 7 ten + 9 ten = 17 ten regroup 17 tens as 1 hundred and 7 ten 1 hundred + 1 hundred = 2 hundred So 178+ 99= 277 Question 2. Estimate: Answer: Explanation: 1. Add the ones 5 ones + 1 ones = 6 ones. 2. Add the tens and hundreds. 9 ten + 4 ten = 13 ten regroup 13 tens as 1 hundred and 3 ten 1 hundred + 6 hundred + 1 hundred= 8 hundred So 695+ 141= 836 Estimate: 840 Question 3. Estimate: Answer: Explanation: 1. Add the ones 7 ones + 6 ones = 13 ones. regroup 13 ones as 1 ten and 3 ones 2. Add the tens and hundreds. 1 ten + 2 ten + 5 ten= 8 ten 3 hundred + 0 hundred = 3 hundred So 327+ 56= 383 Estimate: 380 Add. Use the Commutative Property to check for accuracy. Question 4. Answer: Explanation: No matter in which order you add, the sum is the same. Question 5. Answer: Explanation: No matter in which order you add, the sum is the same. Algebra Add to find the unknown. Question 6. The unknown is Answer: The unknown is 661 + 99 = 760 Question 7. The unknown is Answer: The unknown is 258+ 337= 595 Question 8. The unknown is Answer: The unknown is 739+ 81= 820 Problem Solving Question 9. Mathematical PRACTICE 1 Make a Plan The principal ordered 215 muffins and 155 bagels. How many muffins and bagels were ordered in all? Answer: In total 370 Explanation: The principal ordered 215 muffins and 155 bagels so 215 + 155 = 370 Vocabulary Check Choose the correct word to complete each sentence. reasonable regroup unknown Question 10. To ____ means to rename a number using place value. Answer: regroup Explanation: regroup means to rename a number using place value. Question 11. A missing number is the _____ Answer: unknown Explanation: A missing number is the unknown Question 12. If an answer makes sense, it is _____ Answer: reasonable Explanation: If an answer makes sense, it is reasonable Test Practice Question 13. Mrs. Lewis bought two statues for her garden. One cost$145 and one cost $262. What was the total cost? A.$117
B. $317 C.$407
D. $410 Answer: C Explanation:$145 + $262 =$407
the total cost is \$407

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