ITPEC IP April 2019 Question 3
ITPEC IP April 2019 — Question 3 of 100
There are nine shortest paths from A1 to D4 through C2. The question gives three shortest paths from A1 to C2. From C2 to D4, a shortest route makes one upward move and two rightward moves; the upward move can occur in any of three positions, giving three routes. Thus 3 × 3 = 9.
Answer (b)
Why not others:
- 6 and 12 do not multiply the independent route counts on both sides of C2
- 20 is the total number of unrestricted shortest A1-to-D4 routes, including routes that do not pass C2
Key rule: For paths required to pass a fixed node, multiply the number of shortest paths to that node by the number from it to the destination.
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