Money (and Decimal) Challenge!

The Problem:

(Students had to remind me that we don't have pennies anymore, so I had to make a quick change to the amount - I guess I didn't use debit ALL the time, I would have remembered this on my own).

Working on the Solution:

Our Solutions:

This group had no difficulty with regrouping during subtraction.  They even verified the reasonableness of their solution by performing the opposite operation to ensure accuracy.

 During consolidation, we shared ideas about how to subtract, reminding students that we subtract from the greater amount, rather than the other way around (as seen below).  They encountered some difficulty coming up with an accurate solution on their first try.  Once their misconception was pointed out, they were able to try again and find the answer.

Oops, I cut off the bottom of this chart paper, but if you look closely, this group put our little trick into action for subtracting from a number with a lot of zeros such as $1000.00.  They first subtracted a penny from the thousand dollars, to give themselves $999.99, an easier amount to subtract from (no borrowing and regrouping necessary), then they added the penny on at the end to find their final answer.

This group tried a few different strategies for subtraction.  Although, their method was justified, they made calculation errors that lead them to an inaccurate answer.  As we learned from a group above, it is always a good idea to check the reasonableness of your solution, in this case performing the opposite operation would have alerted them to their error.