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SUBTRACTION

 

 

OPEN NUMBER
LINE

An open number line is a simple way to use number sense in order to subtract. Instead of doing lots and lots of small jumps from one number to the next, counting each jump backwards by one, we can do large jumps using the multiples of 10 or 100 and then subtract the remaining ones. For example; 65-22 is the same as

65-20=45 then 45-2=43, so 65-22=43.

STANDARD
FIND THE
DIFFERENCE

When we are asked to find the difference between two numbers, we are being asked to see how many spaces there are between each number. We can do so by writing both numbers down, and then use an open number line to count the jumps in between.  For example: 71-37 is the same as 37+3=40, 40+30=70 and 70+1=71, so there are 34 jumps inbetween 71 and 37. 

Academic Language

The standard from of subtraction is what most adults were taught in school!  With this method you must start subtracting in the ones place. If the top number is small and the bottom number is large, you then need to exchange 10s for 1 or 100s for 10s, sometimes we call this "borrowing" in order to complete the subraction equation. 

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