We are given two sets $A = \{a, b, c, d\}$ and $B = \{1, 2, 3, 4, 5\}$. We need to determine: i) The number of functions from $A$ to $B$. ii) The number of functions from $B$ to $A$.

Discrete MathematicsSet TheoryFunctionsCardinality
2025/6/7

1. Problem Description

We are given two sets A={a,b,c,d}A = \{a, b, c, d\} and B={1,2,3,4,5}B = \{1, 2, 3, 4, 5\}. We need to determine:
i) The number of functions from AA to BB.
ii) The number of functions from BB to AA.

2. Solution Steps

i) The number of functions from AA to BB.
The cardinality of set AA is A=4|A| = 4, and the cardinality of set BB is B=5|B| = 5.
The number of functions from a set AA to a set BB is given by BA|B|^{|A|}.
In this case, the number of functions from AA to BB is 545^4.
54=5×5×5×5=25×25=6255^4 = 5 \times 5 \times 5 \times 5 = 25 \times 25 = 625.
ii) The number of functions from BB to AA.
The cardinality of set AA is A=4|A| = 4, and the cardinality of set BB is B=5|B| = 5.
The number of functions from a set BB to a set AA is given by AB|A|^{|B|}.
In this case, the number of functions from BB to AA is 454^5.
45=4×4×4×4×4=16×16×4=256×4=10244^5 = 4 \times 4 \times 4 \times 4 \times 4 = 16 \times 16 \times 4 = 256 \times 4 = 1024.

3. Final Answer

i) The number of functions from AA to BB is
6
2

5. ii) The number of functions from $B$ to $A$ is 1024.

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