Posted by Teach3rdgraders on Wednesday, September 22, 2010 at 10:30pm.
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?

3rd grade math  Ms. Sue, Wednesday, September 22, 2010 at 10:36pm
Help needed.

3rd grade  bobpursley, Wednesday, September 22, 2010 at 10:38pm
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. 
3rd grade  Teach3rdgraders, Wednesday, September 22, 2010 at 10:44pm
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.

3rd grade math  kiyuanna Martin, Monday, August 18, 2014 at 6:45pm
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 
3rd grade  Anonymous, Wednesday, March 18, 2015 at 7:06pm
What is greatest perimeter of a rectangle with an area of 39 square feet

3rd grade  krislynn, Thursday, March 24, 2016 at 10:25pm
156