Video: Converting Millimeters to Meters and Writing the Answer in Scientific Form

The length of an object is 7 mm. Express this length in metres, giving your answer in scientific form.

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Video Transcript

The length of an object is seven millimetres. Express this length in metres, giving your answer in scientific form.

Let’s firstly recall some of our conversions of metric units of length. There are 10 millimetres in one centimetre. There are 100 centimetres in one metre. Combining these facts tells us that there are 1000 millimetres in one metre. This means that in order to convert a value from millimetres to metres, we need to divide by 1000. Seven divided by 1000 is equal to 0.007. This means that seven millimetres is the same as 0.007 metres.

This number is not in scientific form as it would need to be written 𝑎 multiplied by 10 to the power of 𝑏, where the absolute value of 𝑎 is less than 10 and greater than or equal to one and 𝑏 is an integer. 0.007 written in scientific notation is seven multiplied by 10 to the power of negative three. This is because the digits have moved three places to get from 7 to 0.007.

We could’ve worked this out directly from the calculation seven divided by 1000. 1000 is the same as 10 to the power of three, or 10 cubed. Dividing by 10 to the power of three is the same as multiplying by 10 to the power of negative three. Once again, we get the answer seven multiplied by 10 to the power of negative three. This is the length of the object in metres.

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