The following simple undirected graph is referred to as the Peterson graph. Which of the following statements is/are TRUE?
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GATE CSE 2022 · Q50
Time

Select all that applyOne or more correct
Solution
Official answer: A) The chromatic number of the graph is 3.; B) The graph has a Hamiltonian path.; C) The following graph is isomorphic to the Peterson graph.
Graph TheoryLet us analyze each statement for the Petersen graph with and :
(A) True: The Petersen graph contains odd cycles (it has 5-cycles, and its girth is 5), so it is not bipartite and requires at least 3 colors. It can be 3-colored (for instance, color the outer 5-cycle with colors and color the corresponding adjacent inner vertices properly with ). Hence, its chromatic number is .
(B) True: The Petersen graph is famous for being non-Hamiltonian (it does not contain a Hamiltonian cycle), but it does possess a Hamiltonian path (a simple path visiting all 10 vertices).
(C) True: The graph shown is a known 3-regular graph with 10 vertices, girth 5, and diameter 2. It is isomorphic to the Petersen graph.
(D) False: The independence number (size of the maximum independent set) of the Petersen graph is , not 3 (e.g., choosing two independent vertices from the outer 5-cycle and two independent vertices from the inner star).
Try the question first, then check your work.
Examiner trap
Recall standard properties of the Petersen graph: it is 3-regular, has 10 vertices, has odd cycles of length 5 (no triangles), contains a Hamiltonian path (but no Hamiltonian cycle), and its independence number is 4.
This Graph Theory previous year question is Q50 of the GATE CSE 2022 paper. Find more GATE CSE PYQs on Graph Theory in Engineering Mathematics, or browse all GATE CSE PYQs.
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Graph Theory has 21 GATE CSE PYQs across 14 papers from 2012 to 2026. 4 of them are 2-mark MSQs like this one, and GATE CSE 2022 has 3.
How GATE tests Graph TheoryIndependent practice explanation verified by the GateAI team. GATE is conducted by the IITs; question text follows the official paper.