Prove It!

Today's math anchor activity asked, "What is the value of 64 tens? How can you prove your answer is correct?"  As students began writing their answers, I pushed them to show their thinking.  This is a hard task for most Third Graders, especially those who have fluid mental strategies.  I was extremely pleased by the variety of strategies students were using to solve this problem.  Here are a few ways students proved their thinking today:

M and A began by counting out 64 tens (the long base-10 blocks in front of them on the rug).  

They quickly realized it would be much faster to count 10 tens, or 100, and show this using the flats.  As they completed this proof, they laid out 6 flats and 4 longs, or 600 + 40.  This hands on strategy is a great way to use a concrete tool for computation of a tricky number!

The above student used a very similar strategy, but showed her thinking using the pictorial form.  She counted the tens under each symbol for base-10 blocks. 

This student used word form and standard form to explain his thinking. Not

pictured is his thinking that included using a number bond to look at 64 tens as 60 and 4 tens.  

Finally, I complimented this student on using his "professor skills" as he wrote a narrative of his thinking.  This is exceptional work and he really put a lot of effort into writing all of his thinking!