AP CSP Day 49: Conditionals Advanced

Big Idea 4: Computing Systems & Networks
Cycle 2 • Day 49 Practice • Hard Difficulty
Focus: Fault Tolerance & Redundancy

Practice Question

A network connects 5 devices with these links: A-B, A-C, B-C, B-D, C-D, C-E, D-E. What is the minimum number of connections that must fail before device A can no longer communicate with device E?

Why This Answer?

Device A connects to B and C. If both A-B and A-C fail, device A is completely isolated and cannot reach any other device, including E. Alternatively, if C-E and D-E both fail, device E becomes isolated. Either way, the minimum number of failures needed is 2.

Why Not the Others?

A) Removing any single connection still leaves alternative paths between A and E (for example, if A-B fails, A-C-D-E still works). C) Two failures are sufficient to isolate either A or E. D) Four failures is more than the minimum needed.

Common Mistake
Watch Out!

Students test only one path and conclude that one failure is sufficient. To find the minimum, you must verify that ALL alternative paths are also broken.

AP Exam Tip

To find minimum failures for disconnection, identify the node with the fewest connections — its degree equals the minimum cuts needed to isolate it. Check both endpoints.

Keep Practicing!

Consistent daily practice is the key to AP CSP success.

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