Maths problem solving!

WALT: add and subtract decimals
Task description: In this activity we are learning how to add and subtract decimals. This is really familiar to a term 1 presentation that I did where if there is a question like 5.9-3.7? Well first I say to myself why sub when I can add and this is how you do it. 

So as I said before if I have a question like 5.9-3.9 I can think and say well what is 3.7 + something = 5.9. Lets start with the whole number 3+2=5. Then 0.7 + 0.2 =0.9 so add all of that together and the answer is 2.2. I always add the things that I added the first time.  

3+(2)=5
.7+(.2)=0.9