  ### Comprehensive & curriculum aligned

In this worksheet, students will need to add two-digit numbers and ones and two-digit numbers and tens mentally. Key stage:  KS 1

Curriculum topic:   Number: Addition and Subtraction

Curriculum subtopic:   Solve Add/Subtract Problems to 100

Difficulty level:   #### Worksheet Overview

In this activity, we will be adding numbers mentally.

Let's remind ourselves what it means to do something mentally.

It means that we work it out in our heads (but don't forget we can always use our fingers to help us!)

We will be adding two-digit numbers with ones and we will be adding two-digit numbers with tens.

Let's have a look at what all this means! A two-digit number is any number made up of two digits, so that's all the numbers between 10 and 99!

Ones are all the one-digit numbers, so that's all the numbers from 0 - 9.

Let's have a look at an example question and how we could answer it:

46 + 7 =

Here are the steps we need to take to answer this mentally:

- Hold up 7 fingers ready to count on

47, 48, 49, 50, 51, 52, 53

We have landed on 53, so 46 + 7 = 53

A two-digit number is any number made up of two digits, so that's all the numbers between 10 and 99!

Tens are all the multiples of tens (which are the numbers in the 10 times tables)

They are 10, 20, 30, 40, 50, 60, 70, 80, 90 and 100.

Let's have a look at an example question and how we could answer it:

46 + 30 =

Here are the steps we need to take to answer this mentally:

- Hold up 3 fingers ready to count on 3 tens

56, 66, 76

We have landed on 76, so 46 + 30 = 76

Remember when we are adding on 10s all the 10s numbers have no ones, so the ones number will always stay the same! Now, let's have a  go at some questions.

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