In a box there are 40 clothes. 20% of the clothes are blue and the rest are…
2023
In a box there are 40 clothes. 20% of the clothes are blue and the rest are white. What is the minimum number of clothes that must be taken without looking in order to be certain that there must be at least two of them which must be white ?
- A.
19
- B.
12
- C.
15
- D.
10
Attempted by 18 students.
Show answer & explanation
Correct answer: D
Answer: 10
Compute the counts: 20% of 40 is 8, so there are 8 blue clothes and 32 white clothes.
To be certain of having at least two white clothes, use worst-case reasoning:
You might pick all 8 blue clothes first (worst case).
After those 8 picks, the next two picks must be white, giving you at least two white clothes.
Total picks needed = 8 (all blue) + 2 = 10.
Therefore the minimum number of clothes that must be taken without looking to be certain of at least two white clothes is 10.