Teach students the basic skill of adding and subtracting with this simple print in place number line calculator, or just use it to save your brain the trouble of another math problem. Also works with exponents.
To work the calculator in addition (it also works in subtraction, too), line the number you want to add up with the plus sign. Look around the upper ring until you find the the number you want to add it with. Right below it should be the answer to the addition problem.
To subtract, line the number you want to subtract FROM (this is on the bottom ring) with the amount you're subtracting (on the top ring). The answer should appear under the plus
Freeing up the calculator
To free the top end of the calculator from the bottom end, take a flat and thin utensil (like a putty knife or xacto) and gingerly work your way in and around the seam until the pices separate.