# Maths

Y3

20.1.21
LI - To be able to add 2- and 3-digit numbers mentally using place value or rounding as a strategy

You are all now becoming experts at solving additions! You have a written method which you can use if you are adding several numbers or 3-digit numbers. You know how to add two 2-digit numbers by partitioning and adding the 1s then the 10s, or by counting on from the larger number in 10s then 1s.

• Today we will be working on the easiest additions of all: ‘no work’ additions where they almost solve themselves! These are often called place-value additions as it is the place value that makes them easy.
•  285 + 200 = 485 Why is this so easy? All we have to do is 200 + 200, the tens and ones stay the same.
• Now look at 285 + 203 =        it is similar to the previous one. Is it still easyCan you work out the answer?  it is still easy: We do  200 + 200 = 400, then we do 85 + 3 =88.
• So the answer is 488!

Y2 Group A - Alice, Jey, Layla, Sana, Eliza, Leonardo, Caroline

20.1.21

LI - To be able to count back in 10s and 1s to solve subtraction (not crossing 10s) and check subtraction using addition, beginning to understand that addition undoes subtraction and vice versa

• Today you will learn about a little trick that you can  use to check your work.
• One of maths’s special tricks is the fact that addition and subtraction are inverse operations. This means you can undo subtraction with addition, and you can undo addition with subtraction. This means you can check your answer and know if you are right or wrong.
• 97 – 75 = 22
• Let's check our answer by using addition. What is 22 + 75 =.
• (Remember 22 is the answer to the subtraction)
• If the answer to the addition is 97 then this means our answer for the subtraction (22) is correct.
• 22 + 75 = 97