Gate 1998
Duration: 2 min
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The video features an educational lecture by Sanchit Jain addressing a specific multiple-choice question from the GATE-1998 computer science exam. The problem asks students to determine the number of functions that can be defined from a set containing m elements to another set containing n elements. The instructor systematically breaks down the problem by first identifying the domain and codomain. He then proceeds to explain the underlying mathematical logic using set diagrams and the fundamental counting principle. The lecture concludes by deriving the correct formula and selecting the corresponding option from the provided choices, which include m+n, m^n, n^m, and m*n.
Chapters
0:00 – 1:48 00:00-01:48
The instructor begins by reading the question text displayed on the screen: 'The number of functions from an m element set to an n element set is'. He underlines the phrases 'm element set' and 'n element set' to highlight the sizes of the domain and codomain. He then draws two vertical ovals on the whiteboard, labeling the left one 'A' with 'm' elements and the right one 'B' with 'n' elements. To illustrate a function, he draws arrows from the elements in set A to set B. He writes 'x 2' next to the arrows, likely using a specific example where n=2 to demonstrate the choices. He then generalizes this by writing 'n x n x n' underneath, indicating that for each of the m elements, there are n choices. Finally, he writes the exponent notation n^m and circles option (c) n^m as the correct answer.
This concise lesson effectively demonstrates how to apply combinatorial logic to set theory problems. The instructor's method of visualizing the mapping process helps students understand that a function requires every element in the domain to map to exactly one element in the codomain. By showing that the first element has n choices, the second has n choices, and so on for all m elements, he clearly justifies the multiplication of n by itself m times. This derivation solidifies the understanding that the base of the exponent corresponds to the codomain size and the exponent corresponds to the domain size, a crucial concept for discrete mathematics and computer science exams.