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WAEC Computer Studies 2021 Paper

Question : 44

Total: 50

Evaluate 10011

_2

_2

Solution:

Concept:

Binary subtraction is done column by column, borrowing

2

from the next left bit whenever needed, just like decimal borrowing of

10

Explanation:

First, write

1111_2

01111_2

so both numbers have the same number of bits.

Now subtract

01111_2

from

10011_2

\begin{array}{r} 10011_2\\ -01111_2\\ \hline 00100_2 \end{array}

Checking with decimals:

10011_2 = 19_{10}

and

1111_2 = 15_{10}

So,

19 - 15 = 4

, and

4_{10} = 00100_2

Answer:

00100_2

— Option B.

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