### Video Transcript

Write the missing digits to
complete the standard algorithm.

And then, we’re shown a calculation
for 93 multiplied by 22. And as part of the working for the
calculation, we can see that there’s a number missing. The arrow’s pointing to it. And we’re given five possible
answers. Five sets of digits, 1800, 1860,
1878, 1980, or 2232. How can we work out the missing
digits?

There are two methods we can use,
and they both involve understanding how the algorithm works or how the method
works. The number that we see in equal
signs at the end is the answer to the multiplication. So, we know 93 multiplied by 22
equals 2046. And how we get there is, first of
all, we multiply both digits in the top number by the ones digit in the second
number. So, in other words, we work out 93
times two.

The second step, then, is to
multiply the digits in the top number by the tens digit in the second number. So, we need to multiply by 20. And this is our missing number, the
answer to 93 times 20. So, our first method to find the
missing digits might be to work out what 93 times 20 is. But, because we know that 186 plus
our missing digits equals 2046, we could rearrange this and work backwards. 2046 take away 186 will leave us
with our missing digits. Let’s try these two methods and
hopefully they’ll both give us the same answer.

Firstly, we could work out 93 times
20. Before we do that, spend 10 seconds
looking at the calculation to see if there’s a quick way to find out what 93 times
20 is. Is there something we already know
that could help us? Yes, in a way, it’s already been
done for us. We know already what 93 multiplied
by two is. If 93 multiplied by two is 186,
then 93 multiplied by 20, or 10 lots of two, will be 10 lots of 186. It’ll be 1860. And if we look across to our
possible answers, we can see that 1860 is there. We didn’t even have to work out the
multiplication. We just shifted the digits one
place to the left and turn 186 into 1860.

Just to be sure and to check our
answer, let’s try the subtraction method, 2046 take away 186. And, we’ll use column subtraction
to find the answer. Six take away six equals zero. We can’t subtract eight from four,
so we’re going to need to exchange. And, there’s a zero in the hundreds
column, so we’re gonna have to exchange from the thousands.

Instead of two thousands, we now
have one thousand. And we could exchange that for 10
hundreds. We’ll take one of those
hundreds. Now, we have nine hundreds, and
we’ll exchange that for 10 tens. 14 tens, then, take away eight
equals six. Nine hundreds take away one hundred
equals eight hundreds. And, then one thousand take away
zero equals one thousand. We’ve checked our answer, and it’s
correct. The missing digits to complete this
standard algorithm are one, eight, six, zero, or 1860.