Video: Evaluating and Comparing Numerical Expressions Involving the Four Operations

Use >, =, or < to fill in the blank in (15 ÷ 5) + 18 _ 8 × 8.

02:51

Video Transcript

Use the symbol for is greater than, is equal to, or is less than to fill in the blank in 15 divided by five plus 18 what eight times eight.

Here, we have two expressions either side of a blank. The expression on the left-hand side contains two operations. There’s a division symbol and an addition symbol in there, 15 divided by five plus 18. And on the right-hand side, we have a multiplication, eight times eight. We need to choose the correct comparison symbol to fill in the blank. Is the first expression greater than the second? Is it the same as the second? Or is it less than the second expression?

We need to find the value of each expression to be able to compare them. Let’s look at the first one to begin with. The first thing that we can see is that there are a pair of parentheses, or brackets, around part of his calculation. What this tells us is like a sign post. The part of the expression that’s inside the parentheses needs to be worked out first. So, what is 15 divided by five? How many fives are there in 15? Well, we know three times five equals 15. So, 15 divided by five has a value of three.

This changes our expression into three plus 18. So, to find the value of 15 divided by five plus 18, we simply need to add three and 18 together to get the answer 21. Now, is 21 going to be greater than, equal to, or less than eight times eight. We can use some number sense here to predict what the answer’s going to be. If we count in eights, it doesn’t take us very long to get to a number that’s greater than 21, eight, 16, 24. And so, whatever the answer to eight times eight, we can predict that 21 is going to be less than it.

Let’s check our prediction by working out what eight times eight is. We know that 10 eights are 80, nine eights is one lot of eight less than this, which is 72. And so, eight eights must be another eight less again, which is 64. Eight times eight is 64. 21 is clearly less than 64. So, we were right when we predicted that the correct symbol to use is the one that represents is less than. 15 divided by five plus 18 is less than eight times eight

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