Question:

The figure below shows the network connecting cities A, B, C, D, E and F. The arrows indicate permissible direction of travel. What is the number of distinct paths from A to F?

Show Hint

Read the arrows from the figure and count the paths backwards from F: the number of paths from a city is the sum of the numbers of paths from the cities it points to.
Updated On: Nov 4, 2026
  • 9
  • 11
  • 10
  • None of these
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The Correct Option is C

Solution and Explanation

Step 1: Read the arrows in the figure:
A \(\to\) B, A \(\to\) D; B \(\to\) C, B \(\to\) D, B \(\to\) E, B \(\to\) F; C \(\to\) E, C \(\to\) F; D \(\to\) C, D \(\to\) E; E \(\to\) F.

Step 2: Count paths to F, working backwards:
From E: 1 path (E-F).
From C: C-F and C-E-F, so 2 paths.
From D: D-C (2 paths) + D-E (1 path) = 3 paths.
From B: B-C (3) + B-D (2) + B-E (1) + B-F (1) = 7 paths.
From A: A-B (7) + A-D (2) = 10 paths.

Step 3: List them to confirm:
Through B: ABF, ABCF, ABCEF, ABEF, ABDEF, ABDCF, ABDCEF (7).
Through D: ADEF, ADCF, ADCEF (2).
Total: 10.

Final Answer:
The correct option is (3): 10.
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