Grade 7 · lesson 1 of 4

Decode four binary places

Use powers of two to translate a small binary number.

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Supplied materials

  • Paper or a note app.
  • Four place values, from left to right: 8, 4, 2, 1. A 1 means include that value; a 0 means leave it out. These are unsigned four-bit numbers.

Learn the idea

Decimal place values grow by factors of ten. Binary place values grow by factors of two, and each digit is either 0 or 1. A bit is one binary digit.

The digits are not individual decimal numbers to concatenate. Add the values of the places with a 1. Leading zeros preserve the four-place format without changing the amount.

  1. Write 8, 4, 2, 1 above four empty places.
  2. Place 1, 0, 1, 1 underneath them.
  3. Add only the included values.
  4. Decode 1101 using the same method.
Worked example

See the method in action

1011 includes 8, skips 4, and includes 2 and 1. Its decimal value is 8 + 2 + 1 = 11.

Your turn

Check your reasoning

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What is the decimal value of unsigned binary 1101?

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See the answer and explanation

13

1101 includes 8 + 4 + 1 = 13 and excludes the 2-place. Reading the characters as the decimal number 1,101 ignores the stated binary place values.

Take it further

Find the four-bit representation of 6. Check: 0110 includes 4 and 2. Then explain why these four unsigned places can represent 0 through 15.

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Longer courses for learners ages 14+

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