3rd grade
posted by Teach3rdgraders on .
Teaching 3rd graders compatable number? Is there a rule? I have taught them to group numbers that add up to ten. I also told them think of it as rounding to nearest 5. Am I steering them in the right direction?

Help needed.

The rule is to choose a near number that is easier to add. Rounding to nearest 5 will work.
For instance, add 3+17+21+12
using compatible numbers
5+15+20+10=50
The use of compatable numbers is an aid to doing arithmetic. It works not as good on multiplying and dividing, but it does give an estimate, but at 3rd grade, you are not there yet. 
Thank you so much. Just adding two digit numbers and in the book there is only one sentence about compatable numbers and wanted to further understand how to teach it to the students since it is in our State Curriculum for third graders to know (TEKS). 683+52 I tell the students 685 will be compatable to 683 and 50 will be compatable to 52 and then add 685+50 = 735.

What are compatible numbers her teacher has her
Round to the nearest number 25,50,75 an the her numbers are 68,39,17,82 
What is greatest perimeter of a rectangle with an area of 39 square feet

156