Wednesday, December 17, 2014

Common Core Explained Simply

Why is Math Different Now from raj shah on Vimeo. Here is another example. Students and parents are complaining why they are not using the standard algorithm for adding, subtracting, multiplying and dividing sometimes... here's why for multiplying and dividing:

Wednesday, December 3, 2014

Why is (-3) squared different than -3 squared?

A great kick off question that sparked a rich conversation. I believe I selected it because students had trouble explaining it on a CPM homework assignment. Another explanation that also explains why a negative multiplied by a positive is negative. For example, -3(6) is equal to 0-3(6) because you can add zero to anything and not change it's value (Identity Property of Addition). Which results in an order of operation problem. 0-3(6). Multiply 3(6) first to get 18. 0 minus 18 is -18.

This problem below demonstrates a students curiosity at the beginning of class and reflecting in the last 5 minutes. (

MARS Task Re-Engagement - Box Plots

While some students were on the East Coast for our sojourn trip, the 8th graders found the 5 important numbers for a box plot using the data of the US Men's soccer team. They found the minimum and maximum (which connects the whisker), median, upper and lower quartiles (half of each half of the data).

I gave feedback such as how could they spread out their data so the box plot wasn't so close together and we also discussed finding the range of the data. The range of the data is the length of the whisker, which is the maximum subtracted by the minimum.

The format was different because the box plot was plotted on a gridded number line, where optimally each square's interval was worth 0.1 or one tenth. 

Another point of confusion was whether to include the median or not when finding the quartiles. When there is an odd number of numbers you do not include the median. If it's even, you would include the median.