NUM016 · Numbers & number systems · Classes 6–12
Binary numbers
Binary is base 2: it uses only the digits 0 and 1. Each place is worth twice the place to its right: 1, 2, 4, 8, 16, …
1101₂Binary numbers
📐 Formula
bₙ…b₁b₀ = bₙ2ⁿ + … + b₁2 + b₀
✏️ Worked example
13 = 8 + 4 + 1 = 1101₂.
🌍 Where it is used
Computers store every number, letter and image as binary.
❓ Quick check
What is 101₂ in base 10?
🏋️ Practice
EasyWrite 6 in binary.
Answer: 110
MediumWhat is 1111₂?
Answer: 15
ChallengeWhat is the largest number 8 binary digits can show?
Answer: 255