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Hexadecimal for GCSE Computer Science

GCSE Computer Science, Data. Usually met in years 9 to 11.

Convert between hexadecimal, denary and binary, and see why hex is a short way to write binary.

What you practise

Starts with single hex digits and builds to converting through binary. Practice moves up a level when a round goes well and down when it does not.

Sample questions

Each sample comes with the method and the reason every wrong option is wrong. Real practice rounds are ten questions at your level.

Sample question, level 2 of 5

What is the hexadecimal number ED in denary?

  1. 237
  2. 27
  3. 153
  4. 222
  5. 224
Show the answer and method

Answer: A, 237

The method: The left digit counts 16s: E = 14, so 14 × 16 + 13 = 237.

Why the other options are wrong:

  • B, 27: The digits were added. The first digit is worth 16 each.
  • C, 153: The first digit was treated as tens. In hex it is worth 16.
  • D, 222: The digits were swapped: the left digit is the 16s.
  • E, 224: The units digit was left out.

Sample question, level 4 of 5

What is the binary number 10110001 in hexadecimal?

  1. B1
  2. 1B
  3. B0
  4. 91
  5. 111
Show the answer and method

Answer: A, B1

The method: Split into two nibbles: 1011 = 11 = B and 0001 = 1 = 1. So it is B1.

Why the other options are wrong:

  • B, 1B: The two nibbles are the wrong way round.
  • C, B0: The last bit was misread.
  • D, 91: One bit in the first nibble was misread.
  • E, 111: Each part was written in denary. Values from 10 to 15 are one hex digit, A to F.

See where this fits: every GCSE option topic and Key Stage 3.

Related topics: Binary, Units and file sizes.