Probability Question 4

Question 4 - 25 January - Shift 1

Let $x$ and $y$ be distinct integers where $1 \leq x \leq 25$ and $1 \leq y \leq 25$. Then, the number of ways of choosing $x$ and $y$, such that $x+y$ is divisible by 5 , is

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Answer: (120)

Solution:

Formula: Probability of occurrence of an event

$ x+y=5 \lambda $

Cases :

X y Number of ways
20
5λ + 1 5λ + 4 25
5λ + 2 5λ + 3 25
5λ + 3 5λ + 2 25
5λ + 4 5λ + 1 25
Total 120