Mental Math and Making Tens
We are taking time to look at adding up to larger numbers, such as 20, by looking for the "making tens facts"
Example:
In 7 + 13
Can I see circle, underline or show somehow that the 7, and 3 digits both rest in the ones place value spot?
Do I know that 7 + 3 = 10 (ten fact)
Do I understand that the number 13 also has 1 ten in the tens place value spot?
Do I understand that my answer needs to be greater than 13 if I am "adding on"?
Do I understand that even if I find a 10 (7+3), I also have to keep the ten in 13?
Do I understand that 2 tens make 20?
As we move forward past grade 1 and 2 - being able to spot those tens, helps us manipulate number relationships for more and more Mental Math capabilities!
Eventually, "tens facts" from 0 to 10 become "making tens" no matter how high the tens count goes, so my mental math can eventually extend to an understanding that:
236 + 14
6 + 4 make 10
3 + 1 make 4 tens (based on their place value)
4 tens and 1 more ten make 5 tens
5 tens is 50
then my answer is 200 + 50 or 250
In this way, we are building capacity for children to see that larger number manipulation can be built up from an understanding of basic tens facts and the meaning of place value!
Although grade 1 curricular expectation for addition and subtraction includes sums and differences between 0 and 20, young children love to play with big numbers and we can help them see all they already know that is hidden inside of larger numbers! They love the challenge and they are still working on the knowledge base they need for grade 1.
For 100 day, we've been practicing all the ways we can organize the amount of material in a large number like 100, so that we can easily count and know we have 100! A lot of this work means a constant, repetitive experience with "making tens"! Such an important fact base for future success manipulating numbers and managing number problems!
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