Truth table reasoning for multi-input logic: an AND gate has 7 inputs. Which single input pattern produces a logic-1 at the output?
-
A0000000
-
B0001111
-
C1110000
-
D1111111
-
ENone of the above
Answer
Correct Answer: 1111111
Explanation
Introduction / Context:AND gates output logic-1 only when all inputs are logic-1. With increasing inputs, the condition for a 1 output becomes more restrictive. This question reinforces the AND truth condition for a 7-input case.
Given Data / Assumptions:
- Gate type: AND.
- Number of inputs: 7 (each input is 0 or 1).
- No inversion or additional logic is present.
Concept / Approach:For an AND gate, output = 1 only if input_1 * input_2 * … * input_7 = 1. In binary logic, multiplication corresponds to logical AND; any 0 forces the product to 0.
Step-by-Step Solution:
List property: AND truth requires all inputs high. Check options: only the pattern with seven 1s satisfies the condition. Therefore select 1111111.Verification / Alternative check:Any pattern containing at least one 0 yields 0 at the output by AND logic definition.
Why Other Options Are Wrong:
Patterns with any 0 (e.g., 0000000, 0001111, 1110000) cannot produce 1 for an AND gate. “None” is invalid because there exists a valid pattern (all ones).Common Pitfalls:Confusing AND with OR; OR outputs 1 if any input is 1, but AND requires all be 1.
Final Answer:1111111