These strips will incorporate both 4 digit addition and subtraction. This is great for getting kids to watch their signs between adding and subtracting. Each strip includes 6 different problems. The first two numbers create the first math problem. Then use that answer to either add or subtract the next number in the strip, until you reach the end. An answer key has been included. Students can work on this independantly or with a partner to compare answers and self check with each other. There are 8 strips, each with 6 different problems. Print off the whole sheet and assign as homework. Cut the strips apart and use in a center.