What's Missing? Missing Numbers in Addition and Subtraction

About This Resource

A complete Grade 2 math lesson pack on finding the missing number in addition and subtraction number sentences to 50: counting on, using the inverse operation, part-part-whole models, fact families and story problems. Includes a lesson plan, worksheet, quiz, homework, A5 flashcards, a rubric, detailed slides with speaker notes, Word files and answer keys.

Overview

Children learn to find the missing number in number sentences such as 17 + ____ = 30 and 42 − ____ = 15. They use a part-part-whole model to see how addition and subtraction are connected, count on from the smaller number, and use the inverse operation to find and check the missing part. They solve number sentences, build fact families and work out missing numbers in story problems.

Resource Details

Subject: Math
Topic: Missing Numbers in Addition and Subtraction
Category: Addition & Subtraction
File Type: PDF
File Size: 324.4 KB
Published: 31 Oct 2026
Downloads: 0

Members Only

Upgrade to Teacher Pro (from ฿199/month) to download this resource.

Upgrade to Pro Login

Looking for something different? Request a Resource.

Grade 2 (ages 7–8) 50 minutes Addition subtraction inverse operations reasoning problem solving

Learning Objectives

Find a missing number in an addition or subtraction sentence to 50.
Use the inverse operation to find and check a missing number.
Solve story problems with a missing part.

How to Use This Resource

Show the slides and model the part-part-whole bar with real objects.
Use the flashcards for quick practice, then complete the worksheet.
Use the quiz to check learning and send the homework home; answers are in the answer keys.

Classroom Activity Ideas

Hidden counters: put 20 counters on the table, hide some under a cup and ask how many are hidden.
Fact family houses: children write the four number sentences for 8, 12 and 20 in a house shape.
Missing number relay: teams race to fill in the blank in number sentences on the board.

Differentiation

Support: use numbers to 20, counters and a part-part-whole mat. Challenge: work with numbers to 100 and write their own missing number story problems.

Assessment

The worksheet and quiz check finding missing numbers (answer keys included). Use the rubric for explanations and story problems.

Teacher Tips

Ask "Do we know the whole or a part?" first. If the whole is missing, add. If a part is missing, subtract or count on. A part-part-whole bar makes this easy to see.

What's Included

10-page printable PDF lesson pack: teacher lesson plan with timings, materials and differentiation
Key vocabulary list (7 words with meanings and examples)
Student worksheet (5 activities)
Quiz / assessment (4 parts)
Homework practice page
Printable flashcards: 7 A5 picture cards (separate PDF)
Assessment rubric (4 levels)
Lesson slides (editable PowerPoint)
Editable Word version of all student pages
Complete answer key (also as a separate PDF)