Video Transcript
Adding Three or More Numbers
In this video, we will learn how to
add three or more numbers where the result is between 100 and 1000.
How could we add these three
numbers? Can you spot a pair of numbers that
are easy to add together? We know that three plus seven makes
10. So, let’s start by adding 23 and
37. We already know that three plus
seven is 10. The two digit is worth 20, and the
three digit is worth 30. So, we can add 20 and 30, which
gives us 50. And 10 plus 50 equals 60. So, we know that 23 plus 37 is
60. Now, we can add our third
number. 60 plus 48 equals 108. An important rule of addition to
remember is that we can add all three numbers in any order. It doesn’t matter which order we
add the numbers; the total remains the same.
How could we add these three
numbers? We could use our knowledge of place
value. We know that two-digit numbers have
a tens digit and a ones digit. We could start by adding the
ones. What is three plus two plus
five? We know that three plus two is
five, and five more makes 10. Now, we can add the tens. Five 10s are worth 50, six 10s are
worth 60, and three 10s are worth 30. 50 plus 60 is 110. 110 plus 30 gives us a total of
140. We’ve added the ones and the
tens. Now, we just need to add our two
totals together. 140 plus 10 gives us a total of
150. 53 plus 62 plus 35 equals 150.
So far, we’ve learned that when
we’re adding three numbers together, we can add in any order. We can use our knowledge of place
value to help us add mentally. First, we can add the ones and then
add the tens and then add both totals together. And we could find an easy pair of
numbers to add first and then add the third number. Let’s practice adding three or more
numbers mentally with a question now.
Fill in the blank: 76 plus 82 plus
68 equals what.
In this question, we have to add
together three two-digit numbers: 76, 82, and 68. What do you notice about these
numbers? One thing you may have noticed is
that two and eight are really easy numbers to add together. This is a pair of numbers which add
together to make 10. So, we could start by adding
together 82 and 68. It doesn’t matter which order we
add our three numbers in. We don’t have to start with the
number 76. We could start by adding 82 and
68. We’ve already added the ones. Two plus eight is 10. And if we add the tens, the eight
being worth 80 and the six being worth 60, we get a total of 140. So, 82 plus 68 equals 150.
Now, all we need to do is add 76 to
150. 150 plus 70 is 220. And now, we can add our ones digit,
which is a six. 220 plus six is 226. When we’re adding three or more
numbers, we can add the numbers in any order. First, we added 82 and 68 because
we knew that two plus eight is 10. So, we knew this was an easy pair
of numbers to add first. The sum of these two numbers is
150. And then all we had to do is add
our third number. 150 plus 76 equals 226.
We can also add three or more
numbers using the standard written method. Instead of writing the sum
horizontally or across the page, we just write the numbers vertically. So instead of adding across, we’re
adding down. We start by adding the ones; then
we add the tens. And if we regroup, we need to add
the hundreds. Let’s try adding three numbers
using the written method now.
Find the result of the following:
64 plus 23 plus 72.
In this question, we have to add
together three two-digit numbers, and we have to use the standard written
method. It doesn’t matter how many numbers
we’re adding together using the written method. We always start by adding the
digits in the ones column. 64 has four ones, 23 has three
ones, and 72 has two ones. So, we need to add four and three
and two. We know that four plus three is
seven and two more makes nine. Next, we need to add in the tens
column. 64 has six 10s, 23 has two 10s, and
72 has seven 10s. So, we need to add together six 10s
plus two 10s plus seven 10s.
It doesn’t matter which order we
add these three digits. We could add six and seven to give
us a total of 13 10s and then add two more 10s. We know that 13 plus two is 15. Six 10s plus two 10s plus seven 10s
is 150 or 15 10s. We found the result using the
standard written method. 64 plus 23 plus 72 equals 159.
Find the result of the following:
234 plus 121 plus 343.
In this question, we have to add
together three three-digit numbers. And we have to use the standard
written method or vertical addition to find the result. We could start by adding the first
two numbers together. So, we would need to add 234 and
121. We’re starting in the ones
column. Four plus one is five. Next, we add the tens. Three 10s and two 10s also gives us
a total of five. And now, we just need to add the
hundreds. Two 100s plus one 100 gives us
three 100s.
Now, all we need to do is add the
third number to the sum of our first two numbers. So, we need to add 343 to 355. Five ones and three ones gives us
eight, five 10s and four 10s gives us a total of nine 10s, and three 100s plus three
100s gives us six 100s altogether. The result of 234 plus 121 plus 343
is 698.
We found the result in two
steps. We added the first two numbers
together, and then we added the third number to the total of the first two
numbers. We could just use the written
method to help us add all three numbers together. In other words, we could just add
these three numbers in one step. We use the same strategy. We start in the ones column. Four plus one plus three is
eight. Then, we add the tens. Three plus two is five, plus four
gives us nine 10s. And finally, we add the hundreds,
two plus one plus three, giving us a total of six 100s.
We found the same result using two
different methods. So, we can add three three-digit
numbers using two steps or just one step. It doesn’t matter which method you
prefer; the result is still the same.
Find the result of the following:
374 plus 217 plus 68 plus 45.
In this question, we need to add
together four different numbers: 374, 217, 68 plus 45. And we can see by the way the
question has been set out that we need to use the written method. It doesn’t matter how many numbers
we’re adding. We always start by adding in the
ones column. So, we need to start by adding
four, seven, eight, and five. It doesn’t matter which order we
add the digits in the ones column. The result will be the same.
We could start by adding seven and
eight, which gives us 15. Then, we can add five more, which
gives us 20, plus four gives us a total of 24 ones. We can write the four ones in the
ones column and the two 10s in the tens column, because 24 has two 10s and four
ones. Now, we can add the tens
column. Again, it doesn’t matter which
order we add these numbers; the result will be the same. We know that six and four makes 10
and seven and one makes eight. 10 plus eight is 18, plus the two
we exchanged gives us a total of 20. And finally, we can add in the
hundreds column. Three 100s and two 100s gives us a
total of five 100s, plus the two we exchanged is seven. The result of 374 plus 217 plus 68
plus 45 is 704.
We used the standard written method
to add together our four numbers. We added the ones, then the tens,
then the hundreds to give us our result of 704.
What have we learned in this
video? We’ve learned that when we add
three or more numbers, we can add in any order. The result is still the same. We also learned that we can add
three or more numbers using either a mental or a written method.
