Let N be the sum of the numbers appeared when two fair dice are rolled and let the probability that N-2,√3N,N+2 are in geometric progression be k 48.…
JEE Main 2023 — Mathematics Probability & Statistics
2023mcqmedium
Let N be the sum of the numbers appeared when two fair dice are rolled and let the probability that N−2,3N,N+2 are in geometric progression be 48k. Then the value of k is
Official previous-year question
Held on 25 Jan 2023 · Verified 6 Jul 2026.
Options
A
2
B
4
C
16
D
8
Did you get this right?
Sign in to track your attempts and accuracy.
Solution
Given,
Two fair dices are rolled,
So total sample space will be n(s)=36
Now given: N−2,3N,N+2 are in G.P.
So, 3N=(N−2)(N+2)
⇒3N=N2−4
⇒N2−3N−4=0
⇒(N−4)(N+1)=0
⇒N=4 or N=−1 (rejected)
Now favourable cases for sum 4≡(1,3),(3,1),(2,2)
So, n(A)=3
Hence, P(A)=363=121=484⇒k=4
Your note
Sign in to keep a private note on this question. Nothing you write is ever public.