Adding and subtracting within 10 (kindergarten) · lesson

Put together

and

Tap each one to count it

💡 To find how many in all, count both groups together.

4 cats and 4 dogs play. Count all the pets. There are 8.

The plus sign, +, means put together.

🧠 How to think about it

Count the first group. Then keep counting the second group. Don't start over.

plus: put together, written +
in all: all of them together

🏡 Try it at home

Put 3 red and 2 green grapes on a plate. How many grapes in all?

Some more come

+

Tap each one to count it

💡 When more come, the group gets bigger, so we add.

3 ducks swim. 2 more come. Now there are 5 ducks.

Start with the first number. Count on the ones that came.

🧠 How to think about it

Ana has 5 crayons and gets 3 more. Say 5. Then count 6, 7, 8. She has 8.

add: put more with a group

🏡 Try it at home

Put 5 toys in a box. Add 2 more. Count on from 5 to find how many.

Take away

−

Tap each one to count it

💡 When some go away, the group gets smaller, so we take away.

There are 4 cookies. Dad eats 1. Now 3 are left.

The minus sign, −, means take away.

🧠 How to think about it

Cover the ones that went away with your hand. Count the ones you can still see.

minus: take away, written −
left: still there

🏡 Try it at home

Put 7 pennies on the table. Take 3 away. How many are left?

Number sentences

+

Tap each one to count it

💡 A number sentence tells a math story with a sign.

3 frogs. 4 more frogs come. That is 3 + 4.

6 apples. 2 get eaten. That is 6 − 2.

🧠 How to think about it

Ask: do they come in, or do they go? Then count each group.

number sentence: numbers and signs that tell a story, like 3 + 4

🏡 Try it at home

Act out 2 + 3 with socks. Then act out 5 − 1. Say each number sentence out loud.

Quick facts

+

Tap each one to count it

💡 You can add and take away small numbers fast, with no picture.

2 + 3 is 5. 4 − 1 is 3. Your fingers can help.

To add, start with the bigger number. Then count on.

🧠 How to think about it

3 + 6? Start at 6, the bigger one. Count on 3: 7, 8, 9. So 3 + 6 is 9.

fact: a quick math answer you know

🏡 Try it at home

In the car, ask quick ones: 2 + 2, 3 + 1, 5 − 2. Use fingers to check.