Tips for Subtraction
The first tips for subtraction is to count backwards if you are subtracting 1, 2 or 3, but after that, use your addition facts. Number families help you grasp this concept:
8 + 5 = 13
13 - 8 = 5
13 - 5 = 8
The second is to addition off the doubles, that helps
18 - 9 = ?
Using the doubles, kids will know that 9 + 9 = 18 and can fill in the blank.
The third is finger counting. When subtracting 15 - 8, students must ask themselves "Open or closed?" With subtraction it is closed. The put their hand in a fist and their palms will say the smallest number ("8"). They will count up to the higher number, which is 15. When they reach 15, they count how many fingers are standing to get their answer.
The last is to use two-Digit subtraction with regrouping. It is a good idea to teach kids when to "borrow" in a subtraction problem. The name of the rule is the "BBB Rule". The BBB rule states "When the BIG number is on the BOTTOM, then you BORROW." For example, 25-6, in which 6 is bigger than 5, so you need to borrow.