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?
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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.
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