Video Transcript
You’re told that thirty-nine times
seven equals two hundred and seventy-three and thirty-nine times thirty equals one
thousand one hundred and seventy. Use this to find thirty-nine times
thirty-seven.
Well in finding thirty-nine times
thirty-seven, you’ll notice in the information we were given we’ve got thirty-nine
times seven and we’ve got thirty-nine times thirty. So that thirty-nine is common to
all of those. Now thirty-seven can be got by
adding seven and thirty. So let’s write a few things
down.
Thirty-seven, as we’ve just said,
is equal to seven plus thirty. So we can rewrite thirty-nine times
thirty-seven as thirty-nine times seven plus thirty. Now we can use the distributive
property of multiplication, and thirty-nine times seven plus thirty means
thirty-nine times seven plus thirty-nine times thirty. And we were told in the question
that thirty-nine times seven is equal to two hundred and seventy-three and
thirty-nine times thirty is one thousand one hundred and seventy. So we can replace these in our
calculation, which means that thirty-nine times thirty-seven is simply two hundred
and seventy-three plus one thousand one hundred and seventy.
And we can quickly do that
addition, so three plus zero is three. Seven and seven is fourteen, so
that’s four carry one. Two and one is three plus the one
we’ve carried makes four. And just one on its own is one, so
the answer is one thousand four hundred and forty-three. And there’s our answer then,
thirty-nine times thirty-seven equals one thousand four hundred and forty-three. But in this case, actually the
answer isn’t the main point of this. The question said use this, so use
the fact that thirty-nine times seven is two hundred and seventy-three and
thirty-nine times thirty equals one thousand one hundred and seventy in order to
find that. So the important part is our
calculation here specifically this bit here showing that you’re using the
distributive property to complete that calculation. And if you wanted to be absolutely
sure of doing the best possible working out, you might actually write down that you
were using the distributive property of multiplication in your working out.
