Two digits run the machine

Computing · Computer Systems · ages 14-15

Name ______________________ Date ____________

Each binary column is worth what compared with its right neighbour?
- One more
- Double
- Ten times
What values can one bit hold?
- 0 or 1
- 0 to 9
- Any letter
The binary number 1011 means 8 + 2 + 1, which is 11.
Circle one: True False
How is 37 written in binary?
- 101101
- 111
- 100101
Read the binary number 1101 as a decimal number. What do you get?
Answer: ______________
What is the largest value 8 bits can hold?
- 256
- 255
- 128
Lee reads 10011011 as 154. What slipped?
- A 1 column was skipped, it is 155
- Binary must be read right to left only
- An extra digit is needed
Read 10110101 as a decimal number. What do you get?
Answer: ______________

Answer key

For grown-ups. Fold this page away before handing over the rest.

Double · Place values double leftward: 1, 2, 4, 8, and on.
0 or 1 · A bit is one on-off choice, so only 0 or 1 fit.
True · The 1 columns are 8, 2 and 1, and they add to 11.
100101 · 37 splits into 32 + 4 + 1, which sets those three columns.
13 · The 1 columns are 8, 4 and 1, which add to 13.
255 · Eight bits count 0 to 255, so 255 is the top.
A 1 column was skipped, it is 155 · Adding every 1 column gives 128 + 16 + 8 + 2 + 1, which is 155.
181 · The 1 columns are 128, 32, 16, 4 and 1, totalling 181.