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