There are 40 socks in a drawer . 70% of the socks are green and the rest are…
2024
There are 40 socks in a drawer . 70% of the socks are green and the rest are blue . What is the minimum number of socks that must be taken from the drawer without looking in order to be certain that at least two blue socks have been chosen ?
- A.
28
- B.
14
- C.
30
- D.
18
Attempted by 12 students.
Show answer & explanation
Correct answer: C
Answer: 30
Calculation and reasoning:
Total socks = 40. Seventy percent are green, so number of green socks = 0.7 × 40 = 28.
To be certain of getting two blue socks in the worst case, assume you pick all green socks first.
If you pick all 28 green socks first, you still need two more picks to obtain two blue socks. So required picks = 28 + 2 = 30.
Therefore, the minimum number of socks that must be taken to be certain of at least two blue socks is 30.