Video Transcript
Find 657.2436 plus
123.64532.
So to solve this problem, the
most common way to do this would be using column addition, and we’re gonna have
a look at that in a second. But also, if we saw this kind
of problem and wanted to try and solve it mentally, there is a method we could
use, because what we could do is first of all take a look at the 657 and the
123. Well, if we add three from the
123 to 657, we get 660. And then, if we add 120, which
is what we have left of our 123, to 660, we get 780.
So now, all we need to do is
add the decimal parts of our numbers, and we can do that using our place
values. So, we’ve got tenths,
hundredths, thousandths. And then, we’ve got ten
thousandths for the first number and the second number we’ve got a hundred
thousandths. So, if we look at the tenths,
we’ve got two and six, which is eight. And then the hundredths, we’ve
got four plus four, which is eight again. Then, we’re carrying this on
for the other place values, and we’d have 892. We get the two because we’d
have zero hundred thousandths in our first number and two hundred thousandths in
our second number. And this will give us our
answer, 780.88892.
Now I did mention that we’re
also gonna show you how to do this with a more formal method, which is using
column addition. So as with any decimal column
subtraction or addition, the key is to line up the decimal points, which I’ve
done here. But I’ve also added in a zero
where we didn’t have a value in one of the place values in the first number,
which is the hundred thousandths. And I’ve just done this just to
avoid confusion.
So first of all, starting from
the right-hand side, we have zero add two, which is two; then six add three,
which is nine; then three add five, which is eight; four add four, which is
eight again; then two add six, which is eight again. Then, we’ve got a decimal
point, which is lined up. Then, we’ve got seven add
three, which is 10. So we’ve put a zero in the
units column, and then we carry one into the tens column. Then, we’ve got five add two
add the one we carried, which gives us eight. And then finally, we’ve got six
add one, which is seven. So therefore, we get the same
answer. So we can say that 657.2436
plus 123.64532 is 780.88892.
