Here are 18 cards I made for Math RTI. The object of this activity is for the student to figure out which numbers are missing from the sequence and then use magnetic numbers to fill in the blank. Each page has 3 number strips on it. I simply printed out the 6 page file onto cardstock, cut the strips apart and laminated them for durability. During RTI, I give each child an number strip and he/she has to dig through the magnetic numbers to find the numbers that are missing from the sequence. This activity covers the numbers 1-25.