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Current time:0:00Total duration:2:37

- [Voiceover] Right
here, we have 65 blocks. And you can count them if you like. But we can represent
them with the number 65. By writing a six in the tens place, we're literally saying
that we have six tens. And this is a 10, this is
a 10, this is another 10, this is another 10, this is a 10, and this is a 10. We have six groups of
ten and that makes 60. And then we have five ones. Five in that orange color. And then we have five ones. And you see them right here. One, two, three, four, five. Now let's do something inter... Well, actually, let me just
first write that down again. Just to emphasize it. We can write down that 65, 65 is equal to six tens, six tens plus five ones. Plus five ones. Now, let's do something interesting. Let's start with 65, so let me write that down again, so we're gonna start with 65. I'm having trouble changing colors. We're gonna start with 65 and I'm gonna subtract... I'm going to subtract 40. I'm going to subtract 40 from that. What am I really doing here? Well, I'm starting with 65, I'm starting with this, and I'm subtracting
four tens and zero ones. Let's subtract four tens from here. Let's subtract one, two, three, four. I took away four of the tens. How many tens do I have left over? Well, I have left over two tens. This is going to be equal to two tens. And how many ones do I have? Well, I still have five ones. So, I still... I still have five ones. And that makes sense. I had five ones, I took away zero ones, so I'm still going to have five ones. What is this going to be equal to? We can write 65. 65. Minus 40. Minus 40 is... Let me do the... I want to do the ones
in that orange color. Minus 40 is equal to, another way of saying two tens is by putting a two in
the tens place, and a... And then we have five ones. A five in the ones place. Two tens plus five ones, or 25.