Door-2-Math Blog

Once Byron, the 4-yr old got the hang of 5 different combinations to add to 10, and that 10 plus any number less than 10 is just that number with ‘teen’ behind it (well, almost anyway, for 1 + 10 is 11, not quite 1-teen; nor is 12 a 2-teen.  But you got the idea), we ready to move on.

Today during the drop off, I moved on to teaching him by borrowing.  The idea is that adding any two numbers that are less than 10, one can always borrow first to make one of the numbers be 10 and then add whatever is left over of the other number.  For example,  8 + 9 is equal to (7+1) + 9 which is 7 + 10 or 7-teen.

The idea behind ‘adding by borrowing’ is that you want to move beyond counting by fingers as soon as possible.  The downfall of counting by fingers is that not only will your child be embarrassed in their teen years, counting fingers will slow their math down so much down the road that inevitably they will grab calculator when they have a chance.  That, of course, will rob them the chance to forming the habit of double-checking by estimation.  You get the drift.

So today, what I was focusing on is to teach Byron adding with 9’s by borrowing 1 from the other number he was adding.  He got pretty good at it.  Asked what he learned about adding with 9’s, he said “just say one less than the number with a teen’.  I think he got the drift.  Onto adding with 8’s next time.

Happy Zen Math!!

(c) Feenix Pan, 2007.  All rights reserved.

04/27/06: Adding with 8’s

Today during the drop off, Byron announced that he is tired to adding with 9’s. I promptly asked him ‘oh, yeah, what’s the trick with adding 9’s?”

“Borrow 1, make ten and add ‘teen’.’ (Not bad for a 4-yr old, I thought).

“Cool! Do you want to know what to do with adding 8?”

“ Then, we are done?” (Boy, he really didn’t want math today).

“Yep.” (I’m a firm believer that there is absolutely no point in dragging a non-thirsty horse to the riverbank!)

“All do you with adding 8 is ‘Borrow 2, make ten and add ‘teen’.”

“that’s it?” (Kids are always amazed that math can be so simple!)

“That’s it with 8. wanna do some tomorrow?”

“of course!” We then moved onto who is doing what at his pre-k grade at the Montessori Schoolhouse.

Happy Zen Math!!

(c) Feenix Pan, 2006.  All rights reserved.

 After Byron got the hang of summing to 6 with different combinations by finger counting, I moved on with him to the 5 combination of summing to 10.

The idea behind becoming familiar with making 10 is that it forms a foundation for speed addition later on. (See the article on Addition: Why Your Youngster’s Math Future Depends on It).

Since making 10 does not have as good of presentation as making 6′s using our fingers, I used his favorite candy: M & M’s.  Restricting to only two colors, I started with 5 blue ones and 5 red ones.  This is a good point to start since each of our hand has 5 fingers

Day 1:  I moved one red one to the blue pile,  thus giving him the visual queue of 4 red + (5 blue + 1 red) = 10 all together.

Day 2:  I moved two red ones to the blue pile, thus 3 red + (5 blue + 2 red) = 10.

You get the idea.

By the end of making-10 sessions, he can recite easily that 7 need 3 to be 10 and 6 need 4 to be 10.

Happy Zen Math!!

(c) Feenix Pan, 2006.  All rights reserved.