Video Transcript
Find 4,762 plus 2,999.
In this question, we’ve got two
four-digit numbers to add together. Now, one way we could find the
answer would be to get a pen and paper to write our two numbers as a column addition
and work it out that way. But we’d need to do a lot of
regrouping if we worked it out this way. Most of our columns would add to a
two-digit number. Instead, there’s a much quicker way
to find the answer. We could actually find the total
really quickly in our heads. To spot how to do this, we need to
look closely at our second number. What’s special about it? Well, although 2,999 looks like a
complicated number to add with all those nines in it, it’s only one away from a very
simple number to add. We could call 2,999 a near multiple
because it’s only one away from a multiple of 1,000.
So to find our answer really
quickly, we could round this second number up to 3,000. So in our heads, we could begin
with 4,762 and then add 3,000 instead. So 4,762 is going to become
7,762. But although that was really easy
to add, it’s not our final answer because if you remember, we rounded 2,999 up to
3,000. In other words, we’ve added one
more than we needed to. So we need to adjust our answer by
taking away one. We didn’t need to use the standard
written method to add these two numbers together. We did it really quickly in our
heads, and this was because we spotted that the second number was a near multiple of
1,000.
We found our answer by rounding
2,999 up to 3,000 and adding that which was really quick to do and then adjusting
our answer by one because we’d added one too many. 4,762 plus 2,999 equals 7,761.
