O-LevelComputer ScienceBoolean logic2210/22 · May/June 2024 · Q87 Marks
A logic circuit is to be built to control the opening of a safe used to store money. There are two keys, A and B, and a time switch C. The safe can only open if both keys are used and the time switch is off. [Table showing input states for key A, key B, time switch C, and safe X (output)]
- (a)Write the logic expression for this problem.[3]
- (b)Complete the truth table for this problem. [Blank truth table with columns A, B, C, X and rows for all combinations of 0s and 1s][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 2024). The mark or mark type is shown in brackets.
- X = (A AND B) AND NOT C
- Four marks for 8 correct outputs
- Three marks for 6/7 correct outputs
- Two marks for 4/5 correct outputs
- One mark for 2/3 correct outputs
- A B C X
- 0 0 0 0
- 0 0 1 0
- 0 1 0 0
- 0 1 1 0
- 1 0 0 0
- 1 0 1 0
- 1 1 0 1
- 1 1 1 0
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