Challenge type: Binary Secrets · Difficulty: ★☆☆☆☆ Easy peasy · Code: A=1, 5 bulbs per letter
Beep has sent you a secret message using light bulbs. A bulb that’s on means 1. A bulb that’s off means 0.
The secret is a word with 3 letters.
The bulbs as 1s and 0s
1: 0 0 0 1 0 2: 1 0 1 0 1 3: 0 0 1 1 1
How to crack it
This message uses the A=1 code. A is 1, B is 2, C is 3, all the way to Z, which is 26. Each letter’s number is written in binary with 5 bulbs. The bulbs are worth 16, 8, 4, 2 and 1.
For each row, add up the numbers above the bulbs that are on. Then find that number’s letter.
| Letter | Number | Binary | Letter | Number | Binary |
|---|---|---|---|---|---|
| A | 1 | 00001 | B | 2 | 00010 |
| C | 3 | 00011 | D | 4 | 00100 |
| E | 5 | 00101 | F | 6 | 00110 |
| G | 7 | 00111 | H | 8 | 01000 |
| I | 9 | 01001 | J | 10 | 01010 |
| K | 11 | 01011 | L | 12 | 01100 |
| M | 13 | 01101 | N | 14 | 01110 |
| O | 15 | 01111 | P | 16 | 10000 |
| Q | 17 | 10001 | R | 18 | 10010 |
| S | 19 | 10011 | T | 20 | 10100 |
| U | 21 | 10101 | V | 22 | 10110 |
| W | 23 | 10111 | X | 24 | 11000 |
| Y | 25 | 11001 | Z | 26 | 11010 |
Need a hint?
The first row is 00010. 2, which makes 2. Which letter is that?
For teachers and grown-ups
Skills practised: Number representation, place value in base 2, and encoding information.
The big idea: Computers store everything, including text, as patterns of 1s and 0s.
Questions to ask:
- Why does each bulb’s value double as you move left?
- What is the biggest number 5 bulbs can show? What about 8?
- Why might computers use 8 bits for each letter?
Take it further: Children encode a short message for a partner using paper bulbs, coloured beads or claps and pauses.