Number Operations: Addition and Subtraction

http://www.mathplayground.com/howto_regroupI.html

Good links  for finding worksheets you can copy for practice:

http://www.math-drills.com/baseten.shtml

http://www.math-drills.com/addition.shtml

Block Shape	Block Name	Size
	1-block /unité	1 unit
	10-block, rod, or long/ la réglette	10 units
	100-block or flat la centaine/la planchette	100 units

Addition:

Soustraction:

Mental Math Strategies for adding and subtracting

1. Using doubles plus one-Children are pretty good knowing their doubles, so if 8 + 8 = 16, then when they come across 8+9...it's like 8+8 and 1 more

It works with tens and hundreds  as well...  If  80 + 80 = 160 (Just add a zero)   then 80 + 90 is like 80 + 80 and 10 more

800 + 900 is like 800 + 800+ 100= 1700 (add 2 zeros)

Doubles plus two - If 6 + 6= 12, then 6 + 8 = 14 is like 6 + 6 and 2 more  6 + 6 = 12 + 2= 14

It also works with 10's and 100's  60 + 60 = 120 so 60 + 80 is like 60 + 60 + 20= 140

and 600 + 800 is the same as 600 + 600 + 200= 1400

2. adding or subtracting 0....there is no change

3. Making 10 ... 9 + 8  take one from the 8 and add it to the 9 to amke 10...10 + 7 = 17...The answer is 17

Making 100.... 80 + 60    80 and 20 more would make 100...so take 20 from the 60 and you have 100 + 40= 140

4. addition strategies

45 + 37  Leave the first number the same. Then add the tens of the next number

45 + 30 = 75 then you have 7 ones left  so 75 + 7= 82

or  add the 10's first then the ones

45 + 37.....40 + 30 = 70....5 + 7 = 12....70 + 12 = 82