Video: Multiplying Numbers up to 999 Including Negative Numbers

Calculate −3(7)(10).

02:14

Video Transcript

Calculate negative three multiplied by seven multiplied by 10.

As multiplication is commutative, we could multiply the numbers in any order. We could start by multiplying negative three by seven. Alternatively, we could multiply seven by 10. Our first step could also be multiplying negative three by 10.

In this question, we’ll work from left to right and start by multiplying negative three by seven. In order to do this, we need to remember what happens when we multiply positive and negative numbers. Multiplying two positive numbers or two negative numbers gives us a positive answer. However, multiplying a positive number by a negative number in either order gives us a negative answer. If the signs are the same, our answer will be positive. Whereas if they are different, the answer will be negative. Three multiplied by seven is equal to 21. Therefore, negative three multiplied by seven is equal to negative 21. The answer is negative as we’re multiplying a negative number by a positive one.

Our final step is to multiply negative 21 by 10. Multiplying any number by 10 moves all the digits one place to the left. So 21 multiplied by 10 is equal to 210. This means that negative 21 multiplied by 10 is equal to negative 210. The calculation negative three multiplied by seven multiplied by 10 is equal to negative 210. We get exactly the same answer if we multiply seven and 10 first. Seven multiplied by 10 is equal to 70. Multiplying this by negative three also gives us negative 210.

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