F.U.N.? stands for Fluency & Understanding Numbers. In Second and Third Grade, the F.U.N.? Empty Number Line can be a great tool for student to visualize operations, for using multiples of 10, counting on, decomposing numbers, understanding the magnitude and position of numbers, beginning fractions, as well as many other concepts. Includes number line hardware, activity guide and 308 cards specific to the Common Core Standards for Grades 2-3, and 30 blank write-on/wipe-off cards.