Why not 10,000?

Ask your student how many perfect squares are less than 10,000. (note: 100*100 = 10,000, so 1 squared up to 99 squared must be less than 10,000. ) Start with your student on the squares of the multiples of ten. 10*10, 20*20, ... 90*90. It's true that a student can get through high school with a calculator and no math facts but it's worth a try to revive some of those forgotten times tables in an interesting way. Eric O'Brien, my mentor at the NC Math Teachers' Circle, gave a weekend workshop a few years back on "Why Not 10,000?". The title refers to the 10,000 math facts between 1*1 and 100*100. Eric advocated for giving students strategies to figure out most of those facts using mental math. Practicing 10*10, 20*20, ... 90*90 makes a start.