Video: Identifying Equivalent Numerical Expressions

Which of the following is equal to 5 × 3? [A] 5 + 3 [B] 8 × 7 [C] 8 + 7 [D] 5 + 7


Video Transcript

Which of the following is equal to five multiplied by three? Five plus three, eight multiply by seven, eight plus seven, or five plus seven.

We can think of this problem as being a little bit like a set of scales that are balanced. On one side, we’ve got five multiplied by three. And on the other side, we’ve got one of the other expressions that’s equal to it, is worth exactly the same. Let’s work out what five multiplied by three is worth. Five multiplied by three is the same as counting in five three times, three groups of five, which we know is equal to 15. And so the question is really asking us, which of the following is equal to 15? Let’s go through each expression and find out which one equals 15.

The first expression on my list is interesting because it involves the same numbers as in the question. Instead of five multiplied by three, we’re given five plus three. Five plus three equals eight. And we know then that five plus three is not equal to five multiplied by three. Sometimes two multiplications can equal the same number. What about eight multiply by seven? Does that equal the same as five multiplied by three? Well, eight multiply by seven is 56, a lot bigger than 15. And so it is not equal to five multiplied by three. What about eight plus seven? We know that double seven would be 14. And so eight plus seven is only one more than that. So we know that eight plus seven equals 15. It looks like this might be our answer. Let’s just check the last pair to see that we are correct. Five plus seven equals 12. And so we can say five multiplied by three equals eight plus seven.

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