Calculate six times eight minus three minus two point six plus three point four.
Now to evaluate this expression, we’ve got to think very carefully about the order
of operations. And to help us to remember those, we’ve got the acronym “PEMDAS”. P stands for parentheses. E stands for exponents. M and D stand for multiplication and division and they both got equal precedence. And A and S stand for addition and subtraction and they’ve also got equal
precedence So the idea is we work our way down that list, picking out whether we’ve got
parentheses, exponents, multiplication and division, or addition and subtraction and do things in
that order. So first of all, let’s look for parentheses. And we do have some parentheses; so we’re
going to have to evaluate the contents of those parentheses first.
So first of all, let’s calculate three take away two point six. Well the
difference between three and two point six is nought point four. We can see that on a number line the jump from two point six up to three is
nought point four. So we can replace three minus two point six in parentheses with just a number
nought point four. So now we’re left with the expression six times eight minus nought point four
plus three point four. So we’ve dealt with parentheses. Are there any exponents or powers or
indices? No. So we’re looking for multiplication and division. And we do have some
multiplication, six times eight. Now six times eight is forty-eight; so we can replace that.
And there is no more multiplication or division; so we’re just left with addition and
subtraction. Now they’ve both got equal precedence and we’d just work from left to right as we do
them. So we’re gonna do forty-eight take away nought point four first of all. So if we start off at forty-eight and take away nought point four, we’re between
forty-seven and forty-eight. And in fact we’re at forty-seven point six, so we can replace these two terms here with forty-seven point six. And that leaves us with forty-seven point six plus three point four.
Now that’s forty-seven point six plus nought point four plus three or plus three
plus nought point four; it doesn’t matter which way around we do it. Well it just so happens if you
look at this forty-seven point six and nought point four, the nought point six and the nought
point four are gonna make a whole one. So I’m gonna go from forty-seven point six plus nought
point four will take me up to forty-eight. Now I need to add the three on as well. So adding
three on is gonna take me up to fifty-one. So our answer is fifty-one.