Originally calculators used seven small lights (or LEDs) to form the digits 0 to 9.
1. Which light is used most?
2. Which light is used least?
3. Which letters of the alphabet could be represented using this system?
4. How many different combinations of 'on' and 'off' can these seven lights make?
Tweet about this starter  Share 
Topics: Starter  Calculator  Investigations  Mixed
How did you use this starter? Can you suggest
how teachers could present or develop this resource? Do you have any comments? It is always useful to receive
feedback and helps make this free resource even more useful for Maths teachers anywhere in the world.
Click here to enter your comments.
If you don't have the time to provide feedback we'd really appreciate it if you could give this page a score! We are constantly improving and adding to these starters so it would be really helpful to know which ones are most useful. Simply click on a button below:
This starter has scored a mean of 3.1 out of 5 based on 24 votes.
Previous Day  This starter is for 23 October  Next Day
1. The lower right light is 'on' for 9 of the digits 09
2. The lower left light is only 'on' for 4 of the digits 09
3. Here's a start:
A could be represented with all lights on except for the bottom light;
B could be all lights on (same as the digit 8);
C could be top, upper left, lower left and bottom;
(If anyone manages to complete this list please share your answers here)
4. There are 2^{7} or 128 different combinations.
Teacher, do your students have
access to computers? 

Here a concise URL for a version of this page without the comments.
Transum.org/go/?Start=October23
Here is the URL which will take them to a related student activity.