Mathematics
Grade 3
15 min
Complete the addition sentence - up to three digits
Complete the addition sentence - up to three digits
Tutorial Preview
1
Introduction & Learning Objectives
Learning Objectives
Find a missing addend in an addition sentence with numbers up to three digits.
Use the inverse operation (subtraction) to solve for a missing part in an addition equation.
Correctly apply place value concepts, including regrouping, when solving for a missing addend.
Check their answer by adding the two addends to verify they equal the sum.
Translate a one-step word problem into an addition sentence with a missing addend and solve it.
Explain the relationship between addition and subtraction using fact families.
You're saving up for a video game that costs 250 tickets at the arcade. If you already have 110 tickets, how many more do you need to win? 🎮
In this lesson, you'll become a math detective! We'll learn how to find the 'mystery...
2
Key Concepts & Vocabulary
TermDefinitionExample
Addition SentenceA math problem that uses a plus sign (+) to show that two or more numbers are being added together to get a total, called the sum.120 + 200 = 320
AddendAny of the numbers that are added together in an addition sentence.In the sentence 120 + 200 = 320, both 120 and 200 are addends.
SumThe answer you get when you add numbers together. It's the total amount.In the sentence 120 + 200 = 320, the sum is 320.
Missing AddendThe unknown number or 'mystery part' in an addition sentence that you need to find.In the sentence 120 + ___ = 320, the blank represents the missing addend.
Inverse OperationAn operation that 'undoes' another. Subtraction is the inverse operation of addition.To solve 120 + ___ = 320, you can use subtraction: 320 -...
3
Core Formulas
Finding a Missing Addend
Sum - Known Addend = Missing Addend
When you know the total (the sum) and one of the parts (an addend), you can find the other part by subtracting the part you know from the total.
Checking Your Answer
Known Addend + Found Addend = Sum
After you find the missing addend, you should always check your work. Add the two addends together to make sure they equal the original sum.
4 more steps in this tutorial
Sign up free to access the complete tutorial with worked examples and practice.
Sign Up Free to ContinueSample Practice Questions
Challenging
I am a missing addend. When you add me to 384, the sum is 750. What digit is in my tens place?
A.6
B.7
C.5
D.3
Challenging
Sam tried to solve 418 - 265 to find a missing addend. He wrote down the answer 253. Why is his answer incorrect?
A.He added the numbers instead of subtracting.
B.He did not regroup correctly from the hundreds place to the tens place.
C.He subtracted 1 - 6 and got 5, which is not possible without regrouping.
D.He aligned the place values incorrectly.
Challenging
A park has 218 oak trees. The town wants to plant more trees until there are 500 trees in total. They plant 150 maple trees. How many more trees do they still need to plant?
A.282
B.350
C.132
D.432
Want to practice and check your answers?
Sign up to access all questions with instant feedback, explanations, and progress tracking.
Start Practicing Free