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CLASS-XI COMPUTER SCIENCE CHAPTER-3 ASSIGNMENT SOLUTION

1. Verify using truth table that X + XY = X for each X, Y in {0,1}

X Y XY X+XY
0 0 0 0
0 1 0 0
1 0 0 1
1 1 1 1

2. Verify using truth table that \( \overline{(X + Y)} \) = \( \overline{X}\overline{Y}\) for each X, Y in {0,1}

X Y X+Y \( \overline{(X+Y)} \) \( \overline{X} \) \( \overline{Y} \) \( \overline{X}.\overline{Y} \)
0 0 0 1 1 1 1
0 1 1 0 1 0 0
1 0 1 0 0 1 0
1 1 1 0 0 0 0

3. Give truth table for the Boolean expression: \( \overline{(X+\overline{Y})} \).

X Y Y’ \( X+\overline{Y} \) \( \overline{(X+\overline{Y})} \)
0 0 1 1 0
0 1 0 0 1
1 0 1 1 0
1 1 0 1 0

4.  Draw truth table for the following equations:
(a) M = N (P+R)

N P R P+R N (P+R)
0 0 0 0 0
0 0 1 1 0
0 1 0 1 0
0 1 1 1 0
1 0 0 0 0
1 0 1 1 1
1 1 0 1 1
1 1 1 1 1

(b) M = N+P+NP̄

N P R NP̄ N+P+NP̄
0 0 0 1 0 0
0 0 1 1 0 0
0 1 0 0 0 1
0 1 1 0 0 1
1 0 0 1 1 1
1 0 1 1 1 1
1 1 0 0 0 1
1 1 1 0 0 1

5. Using truth table, prove that: AB+BC+C= AB+CĀ

A B C Ā AB BC AB+CB+C AB+CĀ
0 0 0 1 0 0 0 0 0
0 0 1 1 0 0 1 1 1
0 1 0 1 0 0 0 0 0
0 1 1 1 0 1 1 1 1
1 0 0 0 0 0 0 0 0
1 0 1 0 0 0 0 0 0
1 1 0 0 1 0 0 1 1
1 1 1 0 1 1 0 1 1

6. State the principal of duality in boolean algebra and give the dual of the boolean expression.

(X+Y).( X’+Z’).(Y+Z)

According to the principle of duality, a true boolean statement or expression can be converted to its dual form by replacing the “0”s in the statement or expression with “1”s, and vice versa and by replacing the “+”s in the statement or expression with “.”s, and vice versa.

The dual form of (X+Y)(X’+Z’ ).(Y + Z)  is (X.Y)+(X’.Z’ )+(Y.Z)

In the above dual expression all the “+”s were replaced by “.”s, and vice versa.

7. Prove the idempotence law of boolean algebra with the help of a truth table

X X Output X.X X+X
0 0 0 0
1 1 1 1

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At Govt. Mizo HSS, he has been instrumental in implementing practical, real-world projects for students—ranging from software development to cloud tools and database applications.

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