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Logic problem 1 of 30

Binary to decimal and back

  • Logic
  • Easy

Without a calculator:

  1. What is the binary number 101101 in decimal?
  2. What is the decimal number 200 in binary?
Show hint

From the right, binary place values are 1, 2, 4, 8, 16, 32, 64, 128. For the second part, take the biggest place value that fits, subtract it, and repeat.

Show solution
  1. 45. The 1s sit in the 32, 8, 4 and 1 places: 32 + 8 + 4 + 1 = 45.
  2. 11001000. 200 = 128 + 64 + 8, so the 128, 64 and 8 places are 1 and the rest are 0.

Check in Python with int("101101", 2) and bin(200).

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