What me? Irrational?
Number Sense
We've found that some students believe that the approximation that their calculators show for irrational numbers is exact.  Here's an activity that you can advertise as long multiplication ...
5.NBT.7 5.NBT 7.NS.3 6.NS.3 8.NS.1 8.EE 8.G 6th 7th 8th 5th irrational numbers square roots multiplication