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Edu-Primes
  • 1 year ago
Transcript
00:00Hi kids, today we are going to use our addition skills to learn more about place value.
00:11We will use place value to help us solve our story problems.
00:14Let's take a look over here and see what problems we have to solve.
00:20There are two classes in the second grade.
00:22Mrs. Jenkins' class has 32 students and Mr. Smith's class has 27 students.
00:27We need to find out how many students are in the second grade.
00:31What do I need to do to find out how many students there are in all?
00:36We need to add these numbers together.
00:39So we are going to add 32 plus 27.
00:43We have double digit numbers here and a really cool way to add these together is to use our
00:47knowledge of place value.
00:50Let's set up these numbers differently so we can see the place value for each number.
00:54Now to make sure we have the numbers in the correct spot let's look at each number.
01:00If we look at the 32 we can see that the 3 is in the tens place and the 2 is in the ones
01:04place.
01:05Looking at the 27 we can see that the 2 is in the tens place and the 7 is in the ones
01:10place.
01:11So do we have them lined up correctly?
01:14Great!
01:16We do have them lined up correctly and now we can use some base 10 blocks to help us
01:20add them together.
01:22So to get 32 we need 10, 20, 30.
01:27Now I have the 3 in the tens place but I still need the blocks for the ones place so I need
01:322 of the ones blocks.
01:35Now on to the 27.
01:37We need to get 27 blocks and we need to start in the tens place.
01:41So here is 10, 20.
01:44Now in the ones place I need 7 of the ones blocks so I get 1, 2, 3, 4, 5, 6, 7.
01:51We can now add these two groups together but to do this we need to be careful and stay
01:55within our place values.
01:57This means that we should not add the tens blocks with the ones blocks.
02:01So we are going to join all our tens place together and then we will join all of our
02:05ones place together.
02:09Now that they are joined together or added together we can now start counting them.
02:13Let's count the ones first.
02:16We have 1, 2, 3, 4, 5, 6, 7, 8, 9.
02:21Now let's count the tens we have 1, 2, 3, 4, 5.
02:27So as we can see here we have 9 ones and 5 tens.
02:32If you look at the math problem over here you will see that 2 plus 7 is 9 and 3 plus
02:372 is 5.
02:38Isn't that really cool?
02:40Now let's look at a different problem.
02:44In this problem we have 47 plus 29.
02:48Let's represent these numbers using our base 10 blocks.
02:51To get 47 how many tens blocks do we need?
02:55How many ones blocks do we need?
02:58If you said 4 tens and 7 ones you are correct.
03:01We need 4 tens blocks and 7 ones blocks.
03:06Now to represent the number 29.
03:09How many tens blocks do we need?
03:11How many ones blocks?
03:14We need 2 tens blocks and 9 ones blocks.
03:18Now we do the same as before and put all of our tens together and all of our ones together.
03:25Let's start by adding our ones together.
03:27We have 1, 2, 3, 4, 5, 6, 7, 8, 9, 10.
03:33Now we need to stop here and remember what we learned about regrouping.
03:36We now have 10 ones which is the same as one of our 10 blocks.
03:42We need to trade these in for a tens block.
03:46Remember we can do this because 10 ones are the same as one of these 10 blocks.
03:52Let's start over and count our ones again.
03:54We have 1, 2, 3, 4, 5, 6.
03:58So we put the number 6 down here under the ones.
04:02Now we can count our tens.
04:03We have 1, 2, 3, 4, 5, 6, 7 tens.
04:08We can put the number 7 under the tens place.
04:1147 plus 29 should equal 76.
04:15We can double check our work by looking at it the way we did before.
04:20If we look at the problem we see that 7 plus 9 is 6.
04:24Wait is that correct?
04:27No 7 plus 9 is 16 but do you remember what we had to do when we counted out the 10 ones?
04:35We used our regrouping skills and traded the 10 ones for one of the blocks of 10.
04:40So we need to look at our tens spot and put a 1 right here.
04:45Because we had to trade the ones for one 10.
04:48So if we add the tens column we get 1 plus 4 plus 2.
04:53What does that equal?
04:56It equals 7.
04:57So 47 plus 29 equals 76.
05:02Great job!
05:03You guys are awesome!
05:05Remember that you will get better at this when you practice.
05:07So keep on practicing, keep learning and we will see you next time.