Day 55 – Solving for Variables

solvevariable.PNG Math 8 – An issue that comes up periodically in math 8 is the need for students to reverse engineer a math statement like “14% of some number is 32.” For some kids they can work backwards using their number sense. Other kids can be helped along by showing them that an easier statement to solve would be “10% of some number is 30” and realize that this is a division question. Lots of other kids simply don’t know what to do.

So today I introduced the idea of “solving for a variable.” We had previously covered some properties such as the multiplicative property of equality, so we had the tools to do this bit of algebra.  My main intent was to show that such an equation can be solved using tools that we know and understand, and that tricks aren’t needed.

Of course next class I saw several kids using some sort of cross multiply strategy…

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