The Power of 10

In first grade, I put a great deal of emphasis on learning combinations of numbers that equal ten.  When I started teaching, I didn't fully understand how important it was for young students to develop fluency with the number 10 and internalize these combinations.  It wasn't until I started tutoring 2nd graders who are behind in math, that I realized how critical it is for students to understand that not only does 5+5=10, but also 8+2 and 7+3 and 3+7.  Because we have a base ten number system, knowing these combinations is actually the foundation for understanding place value, estimation, addition, subtraction, and mental math with bigger numbers.  

Through our Investigations curriculum we have a lot of games that reinforce number combinations up to and equal to ten.  In addition to these games, I have started using transition time to review key facts.  The kiddos really enjoy when I toss a ball and call out a number between 0-10, then they gets to toss the ball back and say the number that will equal 10 (like 1 and 9 or 4 and 6).

I urge the kiddos to "put away their fingers and turn on their brains" to recall these combinations quickly.  I know that the faster and more automatically they can connect numbers to equal ten, the more comfortable they will be to add and subtract.  Once the kiddos have committed these combinations to memory, they are able to use the "get to 10" strategy for adding larger numbers.  For example, in order to quickly add 8+4, the kiddos can "get to 10" by taking 2 from the 4; then they know there are 2 left over so there are 12 all together.  Eventually, the kiddos can also use these primary combinations to add 2-digit numbers, such as 40+60.  If students know that 4+6=10, they know that 4 tens (40) plus 6 tens (60) equals 10 tens (100).

Although we practice these combinations throughout the week, we really work on building confidence and teaching mental math strategies on Fridays.  More to come on our "Fluency Friday"routines and Math Minutes!