Sal breaks the number 18 into 10 and 8. Created by Sal Khan.
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- So knowing place value makes adding subjects easier?(8 votes)
- Would the same idea work for hundreds?(4 votes)
- Yes the same idea should work for hundreds. However if you where to work with monkeys you would have quite a few monkeys on your hand.(8 votes)
- at2:27and2:31in the video, why did sal count 1-8 twice(3 votes)
- Sal probably counted 1-8 twice to focus on that part of the problem and help you focus to understand the problem. :)(3 votes)
- I know what place value means.....Can anybody tell me what a face value means ?(1 vote)
- To take something at face value is an idiom, an expression. It means you believe things are just as they seem. If you take what someone says at face value, it means that you trust what they say.
A face value can also be the number face up on a die.
It can even be a specific amount of money involved in insurance.
Which meaning were you thinking about? How did you encounter the expression?(4 votes)
Voiceover:Let's say that you're throwing a party, and as we all know, any party needs a sufficient number of monkeys. Right now you have 10 monkeys. 1, 2, 3, 4, 5, 6, 7, 8, 9, 10. But you would like to have 18 monkeys. How many more monkeys do you need in order to have 18 monkeys? I encourage you to pause the video and think about it on your own before I work through it. Remember, the goal here is to get to ... The goal here ... Let me write it this way. The goal here is to get to 18, 18 monkeys. Now what do we know about the number 18? Well the number 18, you have this 1 right over here in the tens place. That literally represents 1, 10. And then this 8 represents 8, 1's. Plus 8, 1's. That's the same thing as saying 1, 10 ... 1, 10, that's just a 10 right over there. And 8, 1's, that's just 8. 18 is the same thing as 10 plus 8. If we start with 10 monkeys, which is how many we have started with, how many more do we need to get to 18? Well, if you start at 10, you need 8 more to get to 18. We can verify that visually, if we like. Let's see. Let me copy and paste 1 of these monkeys. Copy. This is 10. Now, let's get to 18. 11, 12, 12, 13, 14, 15, 16, 17, and 18. And 18. How many more did we add? Well, once again, we started, we started with this 10 right over here. Let me box them off. We started with these 10 monkeys. That's 1 group of 10 right over there. We started with the 10. And then we added 8 more monkeys. 1, 2, 3, 4, 5, 6, 7, 8. 1, 2, 3, 4, 5, 6, 7, 8. So we started with 10. We added 8 more monkeys. We added 8 more monkeys to get, to get to 18. And once again, how did we first think about that? Well, 18 is 1, 10 plus 8, 1's. Or 10 plus 8.