As part of the iGCSE, you will be required to convert binary number to and from denary, our base 10 number system.

We’ve already seen that binary uses powers of 2 to convert from Denary (base 10) to Binary (base 2), and using the conversion table below is a useful way to help you to convert as you will not have a calculator in your exam:

128 64 32 16 8 4 2 1

0 0 1 0 1 0 1 0

In the table above, we’ve converted the number 42 into binary by placing the powers of 2 in different columns and placing a 1 under the numbers that you would use to add up to 42. So in this case: 32 + 8 + 2 = 42

We can use this process in reverse to convert a binary number back into denary by writing the powers of 2 over each digit and adding up the columns with a 1 in. If your binary number is longer than 8 digits (bits) just keep doubling the numbers in the columns!

**Task: **Once you have completed the video lesson at the top of the page, download this practice sheet and test your understanding of the conversions. *Use the second page to check your answers.*

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