There are 1000 junior and 800 senior students in a class.And there are 60…
2025
There are 1000 junior and 800 senior students in a class.And there are 60 sibling pairs where each pair has 1 junior and 1 senior. One student is chosen from senior and 1 from junior randomly.What is the probability that the two selected students are from a sibling pair?
- A.
578/34000
- B.
126/48000
- C.
278/79000
- D.
3/40000
Attempted by 16 students.
Show answer & explanation
Correct answer: D
Given:
Total junior students = 1000
Total senior students = 800
Sibling pairs (1 junior + 1 senior each) = 60
Step 1: Find total ways to select 1 junior AND 1 senior:
= 1000 × 800 = 800000Step 2: Find favorable outcomes (both selected belong to same sibling pair):
= 60 (only 60 valid sibling pairs exist)Step 3: Calculate probability:
= 60/800000
= 3/40000
≈ 0.000075Answer = 3/40000