18 take away six equals what?
In this problem, we start with 18. This symbol here means to take away. And so, we start with 18. And then, we take away six. What’s left? Let’s look at two different ways we could find the answer.
The first way we could find the answer is by using equipment to help us. We could model the number 18 as one lot of ten and eight ones because we know one ten and eight ones are the same as 18. So now we’ve made 18 in this way, we can take away six. Let’s count the six ones as we take them away: one, two, three, four, five, and six. We started with one ten and eight ones and we took away six ones. What have we got left? One ten, but only two ones. We have 12 left.
We could work out the same answer in our heads. We start with 18. And we remember that we can break up 18 into two parts, 10 and eight, because 10 add eight makes 18. Now, what we need to do is to take away six. Which part of 18 should we take away six from quickly, the 10 or the eight? Let’s take away from eight because they’re both groups of ones. What is eight ones take away six ones? Well, eight take away six leaves us with two.
Although we’re not using equipment this time, we can see that’s exactly what we’ve just done using the cubes. Eight take away six equals two. Now we’ve taken away six, all we have to do is to put our parts back together to find the answer. 10 plus two equals 12. And so, we’ve done in our heads exactly what we did using the cubes. We combined one ten with two ones to find the answer 12.
There are lots of methods we could use to find the same answer. 18 take away six equals 12.