How the clock taught Gab to multiply

Gab learned to multiply by accident. I haven’t taught him about multiplication yet except for the idea that it is repeated addition.  I only showed him a few examples like 2×3 is just like 2+2+2 and 3×3 is just like 3+3+3.  I only taught him this concept. Nothing else.

Gab has finished Mastering Basic Math Addition when he asked me if 5 x 8 is equal to 40. I said, “Yes it is.” Then he asked if 5 x 9 is 45. And I said, “Yes.”

Hey, looks like he is up to something.  But how did he know this?

So I asked him if he knows what is 5 x 6? He quickly said 30! Then he confidently tells me that 5 x 12 is 60!

He told me all of these even if I haven’t started teaching him about multiplication yet. Basic multiplication is usually for a Grade 2 and Grade 3 curriculum. Yet here I am talking multiplication by 5 with a six year old.

So I asked him, how did you know about multiplying by 5?

He quickly said, “The clock!”

My jaw dropped. He figured it out by himself. The hour hand and the minute hand of the clock are related by a factor of 5. When the hands point to the number 1, it is 5 minutes. If it points to 2, it is 10 minutes. If it is 3, it is 15 minutes and so on and so forth.

Our wall clock that teaches multiplication by 5. 😛

Thus, Gab knows multiplication by 5.

But wait there is more!

Gab then told me that 15 x 4 is 60! Which is correct! While still using the clock, he figured out that each quarters (the labels 3, 6, 9 and 12) is related by a factor of 15.  From here, he also knows how to multiply by 15.

So I gave him more tips on multiplication.

I told him that multiplying by 0 is still 0.  Thus he now knows how to multiply by 0.

I also told him that multiplying by 1 is just equal to the number itself.  Thus he now knows how to multiply by 1.

I told him that multiplying by 2 is just like adding doubles. He now knows how to multiply by 2.

And finally, multiplying by 10 is just like skip counting by 10. He now knows how to multiply by 10.

In just one night, Gab learned x0, x1, x2, x5, x10 and x15 just because of a clock!

Now, we are learning multiplication for the remaining of the numbers. We are using the method called Number Sense in learning multiplication.  This method doesn’t let us memorize the multiplication table like how I was taught in grade school. Instead, by knowing the relationship between numbers we can arrive at the answer by decomposing and regrouping these numbers.

I will discuss more about Number Sense in another post. But for now, I am happy that we are learning multiplication without the fear and intimidation.

Thanks to the clock!