Binary conversions

Published

September 19, 2025

Modified

September 30, 2025

Question 1

Convert the following binary numbers to decimal:

  • 1001
  • 1101101
  • 1000001
  • 1111111
  • 100000011000001
  • 101010101010101
  • 110101
  • 10101100
  • 11111010001

Check your answers (you can google search “1001 binary to decimal” or similar to get an answer)

Binary Calculation Decimal
1001 2³ + 2⁰ 9
1101101 2⁶ + 2⁵ + 2³ + 2² + 2⁰ 109
1000001 2⁶ + 2⁰ 65
1111111 2⁶ + 2⁵ + 2⁴ + 2³ + 2² + 2¹ + 2⁰ 127
100000011000001 2¹⁴ + 2⁷ + 2⁶ + 2⁰ 16577
101010101010101 2¹⁴ + 2¹² + 2¹⁰ + 2⁸ + 2⁶ + 2⁴ + 2² + 2⁰ 21845
110101 2⁵ + 2⁴ + 2² + 2⁰ 53
10101100 2⁷ + 2⁵ + 2³ + 2² 172
11111010001 2¹⁰ + 2⁹ + 2⁸ + 2⁷ + 2⁶ + 2⁴ + 2⁰ 2001

Question 2

Convert the following decimal numbers in binary: - 33 - 58 - 263 - 3450 - 9349 - 724

Decimal Calculation (Powers of 2) Binary
33 32 + 1 = 2⁵ + 2⁰ 100001
58 32 + 16 + 8 + 2 = 2⁵ + 2⁴ + 2³ + 2¹ 111010
263 256 + 4 + 2 + 1 = 2⁸ + 2² + 2¹ + 2⁰ 100000111
3450 2048 + 1024 + 256 + 64 + 32 + 16 + 8 + 2 = 2¹¹+2¹⁰+2⁸+2⁶+2⁵+2⁴+2³+2¹ 110101111010
9349 8192 + 1024 + 128 + 4 + 1 = 2¹³ + 2¹⁰ + 2⁷ + 2² + 2⁰ 1001001000101
724 512 + 128 + 64 + 16 + 4 = 2⁹ + 2⁷ + 2⁶ + 2⁴ + 2² 1011010100

(263)10 = …

Quotient Remainder
131 1
65 1
32 1
16 0
8 0
4 0
2 0
1 0
0 1

(3450)10 = …

Quotient Remainder
1725 0
862 1
431 0
215 1
107 1
53 1
26 1
13 0
6 1
3 0
1 1
0 1

Reading from bottom to top: 1101 0111 1010

(9349)10 = …

Quotient Remainder
4674 1
2337 0
1168 1
584 0
292 0
146 0
73 0
36 1
18 0
9 0
4 1
2 0
1 0
0 1

Reading from bottom to top: 10 0100 1000 0101

Question 3

Consider a 32-bit CPU: a. How many numbers can be represented on this CPU? b. What’s the largest unsigned number (positive numbers only)? c. What’s the largest signed number?

  1. 4,294,967,296 (232)
  2. 4,294,967,295
  3. 2,147,483,648 (231) Note that for signed numbers, one bit is reserved for the sign (+/-).

Question 4

What’s the smallest number which requires 12 bits?

212 = 4096 Note: Any number smaller than 4096, doesn’t require 12 bits to be represented in binary. 4096 is the smallest number which requires 12 bits.

Question 5

What’s the minimum numbers of bits required to store the value 16587.

  1. Represent the number in binary: 100 0000 1100 1011
  2. Count the number of bits required to represent this number.

The answer is 15 bits.

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