Addition to 50 with second addends >10

General

Students learn to add to 50 with second addends that are greater than 10.

Relevance

It is important to be able to add to 50 so you know how to combine amounts in larger quantities.

Introduction

Ask students to calculate the total of an addition problem on a number line. You can count with steps of 1, or calculate the answer in one big step.

Development

Discuss with students the importance of being able to add to 50. Repeat & refresh their prior learning about tens and ones. The learning goal is presented in visual, abstract and story form. You can choose the form that best fits your class by using the menu in the bottom right of the page. In the visual explanation, count the objects. Show students how they can count two sets of objects together. Emphasize that they first add to make ten, and then count on with the ones. Practice a few visual problems with the students as a class. For the abstract, show that you can solve the addition problems without visual support by using other methods. Demonstrate by doing an addition problem with the class on the number line. Show two more methods and practice them with the class. Practice a few abstract problems with the class and ask students which method they chose. Finally remind students of the steps you take to solve a story problem. Practice solving a story problem as a class.

Check that students understand addition to 50 with second addends larger than 10 by asking the following questions:
- Why is it useful to be able to add to 50?
- Which method do you use to calculate an addition problem to 50?

Guided practice

Students first practice an addition problem with visual support. They then get an abstract problem to solve and finally a story problem.

Closing

Check that students have understood the learning goal by asking students which method for adding to 50 they like best. Students must then practice a few addition problems as a class. Ask students which method they used, and make sure to point out that all methods are useful as long as they work for you. The final exercise can be done as a class, in groups, or in pairs. Give students cards with addition problems with totals to 50 with second addends greater than 10. Can the student solve the addition problem shown? Then they get point. The student with the most points wins.

Teaching tips

Students who have difficulty adding to 50 can start by practicing adding to 30. They can also be supported by the use of manipulatives, like erasers, pencils, or blocks to help visualize the addition. They can also make use of the number line.