Subtract Doubles
šÆāāļø Doubles to the rescue! If you know your addition doubles by heart, then you automatically know your subtraction doubles for free!
Concept
A "double" is an addition fact where both numbers are exactly the same, like 5 + 5 = 10, or 8 + 8 = 16. šÆ **The "Un-Double" Strategy:** Because addition and subtraction are opposites, you can use doubles to solve subtraction! **Example: 14 - 7 = ?** Does the number 14 make you think of a double? Yes! You know that **7 + 7 = 14**. If 7 + 7 equals 14, then if you take one of those 7s away, you must have the other 7 left! So, **14 - 7 = 7**. If the number you are subtracting is exactly *half* of the starting number, the answer is just the same number again!
Try it
Let's un-double some numbers! **Instructions:** Think of the addition double to find the subtraction answer! **Problem 1: 12 - 6 = ?** * What double makes 12? ( ___ + ___ = 12 ) * Answer: 12 - 6 = ___ **Problem 2: 16 - 8 = ?** * What double makes 16? * Answer: 16 - 8 = ___ **Problem 3: 18 - 9 = ?** * Answer: ___ **Problem 4: 10 - 5 = ?** * Answer: ___