# Light Bulb Binary

Light Bulb Binary
Background and Preparation
Here’s an easy way to explore binary, a number system based on two
(bi- = 2).
You Need:
Worksheet—Light Bulb Binary handout
Scissors
Introduction and Preparation
Students easily associate our decimal number system with the
number ten. Ask the meaning of the root dec- (dec- = 10). Have
students tell how many numerals we use in our decimal system (ten:
0, 1, 2, 3, 4, 5, 6, 7, 8, and 9).
Discuss the root bi- = 2 and come up with some related words
(bicycle, biceps, bipedal, . . .). Connect bi- with the word binary.
Pass out Light Bulb Binary worksheets. Have students cut along the
dotted lines to get five pairs of light bulbs. Fold on the solid lines to
create five light bulb cards with an “off” light bulb on one side of the
card and an “on” light bulb on the other.
Tell students that you’re tossing out all the numerals in the world
except for two: 0 and 1.
Discuss how an electrical circuit only has two settings: “off” or “on.”
Write on the board: off = 0
on = 1.
Have students note that the “off” light bulb card is labeled “off 0.” The
“on” light bulb card is labeled “on = 1.” Binary is used in computers
because electricity can be either on or off, nothing else.
Place Value: Decimals, Binary
Now introduce the place value chart. Since our decimal system is
based on 10, you start with a 1 in the ones place, multiply by 10 and
get the tens place, multiply that by 10 and get the hundreds place,
and so on:
Decimal Place Value
10,000
1,000
100
10
1
Binary place value works the same way. Start with a 1 in the ones
place. Multiply 1 by 2 and get the twos place. Multiply 2 by 2 and get