Start with a math puzzle from Martin Gardner’s Entertaining Mathematical Puzzles:

THE SILVER BAR

bar of pure silver, 31 inches long,

cut the bar into smaller pieces

give the lady an inch of the bar

on each succeeding day he would add another inch to her amount of silver

keep this silver as security

prospector expected to be able to pay his rent in full, she would return the pieces to him

March has 31 days

cut it into 31 sections, each an inch long

prospector wished to carry out his agreement with the fewest possible number of pieces

determine the smallest number of pieces into which the prospector needs to cut his silver bar

Pick a 4-digit number and break it down in base 10 (highlight how many symbols were available to us and how in base 10 the highest symbol is 9 and in base-5 the highest symbol is 4)
Then we do the same thing in binary ie base-2. Break down the number “44”

Represent “44” in base-6
Represent the current year in base 5
Show how you can represent any number up to 63 on one hand in binary
Spell their name in binary using a cipher (ie A = 1, B = 2…Z = 26)
Bridge this to ASCII so they understand that physical inputs like a keyboard stroke is converted to binary which a processor can understand! Computers do calculations in binary because electrical signals on a chip are either on or off. So representing numbers can be thought of like a morse code of “on”/”off” at light speed or something.