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units of 10

My cousin is the mother of a first grader and she called me this week because she could not understand what he had to do for his homework. Said cousin is a college graduate and successful business woman, but she could not understand the work of her six year old son.

Say hello to the Common Core!

The most recent shift in education has been a fight of quality over quantity. The belief is that if we focus on children understanding a few core ideas really well, instead of being familiar with many different concepts then they will be armed with a deeper mathematical understanding that provides them the skills to problem solve everything.


Back to the homework. Each question on the homework had two ten frames to represent numbers above ten (14, one filled ten frame and one ten frame with 4 slots filled in). The homework asked for subtraction but asked for students to subtract by going back to the landmark number. A landmark number is a number that is easy for you to add to/subtract from (generally it is 5 or 10). It is a safe jumping off point and an easy point to reference. Rather than just subtracting 8 from 13, students had to subtract enough to get back to 10 and then subtract the rest.

Are you still with me? It would look like this: 13-8, let's first get to our landmark number so we will subtract 13-3=10.

Now we need to subtract the rest, if we already subtracted 3 of the 8 we are subtracting then we have to subtract another 5 (because 8-3=5).

10-5=5

Our answer is 5.


If you are anything like my cousin you understand what I did but you find this to be overcomplicating the subtraction problem and adding in an extra step where it is unnecessary.

Understandable, but this school of thought provides your child with a solid foundation of understanding that numbers exist in units of 10. It gives them the ability to manipulate numbers so that they can go back to their ten-fact knowledge to accurately problem solve most any challenge presented to them. If a child knows their facts within 10, their conceptual understanding of addition, subtraction, regrouping and many other fundamental math skills will be a breeze.


Ideal for ages 5-7

Here is a ten frame that shows the number 6, which can also be identified as 5 and 1 more.

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