Question:medium

Out of \(100\) students, two sections of \(40\) and \(60\) are formed. If you and your friend are among the \(100\) students, what is the probability that (a) you both enter the same sections? (b) you both enter the different sections? 

Updated On: Jan 23, 2026
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Solution and Explanation

Given:

Total students = 100
Two sections are formed of sizes 40 and 60
You and your friend are two particular students among the 100


Total possible cases:

After you are placed in a section, your friend can go into any of the remaining 99 positions.

So, total possible cases = 99


(a) Probability that both enter the same section

Case 1: You are in the section of 40 students
Remaining students in that section = 39

Case 2: You are in the section of 60 students
Remaining students in that section = 59

Total favourable cases =

39 + 59 = 98

Probability =

98 / 99


(b) Probability that both enter different sections

Favourable cases =

Total cases − Same section cases

= 99 − 98

= 1

Probability =

1 / 99


Final Answers:

(a) Probability that both enter the same section = 98 / 99
(b) Probability that both enter different sections = 1 / 99

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