O-LevelComputer ScienceBoolean logic2210/11 · May/June 2020 · Q29 Marks
Consider the logic statement: X = (((A NAND B) OR (B XOR C)) AND NOT C)
- (a)Draw a logic circuit to match the given logic statement. All logic gates must have a maximum of two inputs. Do not attempt to simplify the logic statement.[5]
- (b)Complete the truth table to represent the given logic statement. A B C Working space X 0 0 0 0 0 1 0 1 0 0 1 1 1 0 0 1 0 1 1 1 0 1 1 1 [4]
This question uses a diagram from the original paper, which isn't shown here. Open the full paper from the past papers archive to see it.
Mark scheme
Marking points from the official mark scheme (May/June 2020). The mark or mark type is shown in brackets.
- [5] 2(a) (Diagram showing gates: NAND for A,B; XOR for B,C; OR for NAND and XOR outputs; NOT for C; AND for OR and NOT outputs, leading to X) 1 mark for each correct gate.
- [4] 2(b) (Truth table with X column: 1, 0, 1, 0, 1, 0, 1, 0) 4 marks for 8 correct outputs; 3 marks for 6 or 7 correct outputs; 2 marks for 4 or 5 correct outputs; 1 mark for 2 or 3 correct outputs.
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