 Recognizing subtraction problems to 5

# Recognizing subtraction problems to 5

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## General

Students learn to recognize subtraction problems and match them to the images shown.

K.OA.A.5

## Relevance

Discuss with students that it is useful to be able to recognize from images when you have a subtraction problem. You learn to recognize subtraction problems which you need to be able to solve them easily.

## Introduction

Show different amounts of objects on the interactive whiteboard. Ask students where the correct amount is given. Ask students to count the amounts out loud and circle the correct amount.

## Development

The interactive whiteboard shows a birthday cake. Some candles are lit, and others have been blown out. First count how many candles there are in total. Then count how many candles have been blown out. There are 5 candles, and 1 has been blown out. The candle that has been blown out is taken away, so the subtraction problem is 5-1. Discuss all the versions of the cake and show the matching subtraction problems. Then show the hamburgers. Count the 5 hamburgers together. 1 hamburger is eaten. Emphasize that when you say that something is subtracted, or taken away, you use the minus sign - which shows that the second number is taken away from the first number. Discuss that the whole number is the first minuend, and the number that is taken away is the subtrahend.
Next show a fish tank from which fish are being taken out. Ask the students which image matches the subtraction problem shown. Erase the grey boxes to uncover the answer. Next there is a tree with oranges and students must determine which subtraction problem matches the image. Ask them to write the answer and hold them up. Check their work. Then discuss, using hamburgers, that if they have determined what the subtraction problem is, they can take the second away from the first to determine the difference. The difference is what remains when you take the second minuend away from the first. If you take away the hamburgers you have eaten from the total number of hamburgers, you know how many hamburgers are left. Practice with the example of light bulbs to see if students are able to solve the answer.

Check that students are able to recognize subtraction problems to 5 by asking the following questions:
- How do you know which numbers are in the subtraction problem?
- What do you do first to determine how much is left when you take one number from another?
- What is the first minuend in a subtraction problem?
- What is the subtrahend in a subtraction problem?

## Guided practice

Students first practice recognizing subtraction problems by matching the images to the subtraction problems, and then they are asked to not only match, but also determine the answer to the subtraction problem.

## Closing

Discuss with students that it is important to be able to use an image to determine a subtraction problem, so you better understand what subtraction is. Check that students are able to match images to subtraction problems to help solve for the answer. A subtraction problem is given on the interactive whiteboard, students must drag chocolates to form images that match the problem given.

## Teaching tips

Students who have difficulty subtracting using visual support can be supported by the use of MAB blocks or other manipulatives. Have the student set out the blocks to represent the total, and then ask them to take away the subtrahend. Then have them count how many are left in the original pile.

## Instruction materials

Optional: MAB-blocks or other manipulatives

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