PYQ Vault
EbooksTutor

Three numbers chosen from 1 to n: probability they form an increasing AP or GP

This type of question, asked 2 times: 2 Apr 2025, 4 Apr 2026 S2. All 2 questions below, oldest first.

Try each one first, then open its answer.

  1. Question 1

    2 Apr 2025

    74
    Three distinct numbers are selected randomly from the set {1,2,3,……,40}\{ 1,2,3,\ldots\ldots,40\}. If the probability, that the selected numbers are in an increasing G.P. is mn\frac{m}{n}, gcd(m,n)=1gcd(m,n) = 1, then m+nm + n is equal to

  2. Question 2

    4 Apr 2026 S2

    71
    From a month of 31 days, 3 different dates are selected at random. If the probability that these dates are in an increasing A.P. is equal to ab\frac{a}{b}, where a,b∈Na,b \in N and gcd(a,b)=1gcd(a,b) = 1, then a+ba + b is equal to ____\_\_\_\_ .