Practise 60 real questions on Boolean algebra and logic circuits from 2021 to 2026. See the answer and explanation as soon as you answer.
Boolean algebra and logic circuits is one of the 10 main topics in our A Level Computer Science (Cambridge (CAIE) 9618) question bank, and about 5% of its real questions come from it. Tayyari Karo has 60 real questions on this topic from 2021 to 2026, from Paper 1, Paper 3. By difficulty: 27 hard, 25 medium, 8 easy.
Work through the questions below, then open the explanation for each one. Redo the ones you missed a few days later.
These are real past-paper questions. Think of your answer first, then open the explanation.
Write the Boolean expression from your answer to 6(c)(i) as a simplified sum-of-products. Do not carry out any further simplification. [2]
A.B + B.D + C.D (terms in any order). MP1 one correct term with an OR sign; MP2 all three correct terms connected by OR and no other terms.
Each loop gives a product term.
Write the Boolean expression from your answer to part b(ii) as a simplified sum-of-products.
A.B + B.C + A.B.C
Two marks for correct expression.
(c)(ii) Draw loop(s) around appropriate group(s) to produce an optimal sum-of-products.
Groups of 2 or 4 ones circled to cover all 1s.
2 marks: 1 for each correct loop.
(b) Write logic expressions for the security system.
Floodlight X = 1 if: security on AND daylight low AND person detected within 2m.
Audio alarm Y = 1 if: security on AND (one or more doors open OR person detected within 2m).
X = E AND A AND C
Y = E AND (B OR C OR D)
2 marks: 1 for each correct expression.
(d)(ii) Use Boolean algebra to write your answer to part (d)(i) in its simplest form.
T = D.(A.B)
1 mark for simplest form.
(c) Write the Boolean logic expression from your answer to part (b) as a simplified sum-of-products.
Z = AC + BC (or equivalent correct simplified expression)
2 marks: 1 for any correct Boolean term, 1 for correct and complete expression.
(b) Simplify the given Boolean expression using Boolean algebra. Show your working.
Y = A.B.C.D + A.B.C.D + A.B.C.D + A.B.C.D
Working:
Y = A.D.(B.C + B.C + B.C + B.C)
Y = A.D.(B.(C + C) + B.(C + C))
Y = A.D.(B.(1) + B.(1))
Y = A.D.(B + B)
Y = A.D.(1)
Simplified: Y = A.D
3 marks: 1 for correct working from points, 1 for correct answer.
(a) Write the Boolean expression as a sum-of-products.
Z = A.B.C.D + A.B.C.D + A.B.C.D + A.B.C.D + A.B.C.D + A.B.C.D
3 marks: 1 per two correct products to max 3.
| Session | Paper 1 | Paper 3 |
|---|---|---|
| May/June 2026 | 2 | 4 |
| May/June 2025 | 2 | 4 |
| October/November 2025 | 2 | 4 |
| May/June 2024 | 2 | 5 |
| October/November 2024 | 1 | 5 |
| May/June 2023 | 2 | 4 |
| October/November 2023 | 2 | 2 |
| May/June 2022 | 2 | – |
| October/November 2022 | 2 | 3 |
| May/June 2021 | 1 | 3 |
| October/November 2021 | 3 | 5 |
60 real A Level Computer Science (9618) questions on Boolean algebra and logic circuits from 2021 to 2026, from Paper 1, Paper 3. Each one shows the year, session and paper it came from.
Yes. Every question shows the correct answer and a short explanation the moment you answer.
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