Maximum attempts to draw a red pair of shoes
Question
Raj has ten pairs of red, nine pairs of white and eight pairs of black shoes in a box. If he randomly picks shoes one by one (without replacement) from the box to get a red pair of shoes to wear, what is the maximum number of attempts he has to make ?
Options
27
36
44
45
Explanation
To determine the maximum number of attempts (the absolute worst-case scenario), we must assume Raj draws every single non-red shoe, and then draws single mismatched red shoes before completing a pair .
Convert shoe pairs into individual units: Red shoes = 10 × 2 = 20 units . White shoes = 9 × 2 = 18 units . Black shoes = 8 × 2 = 16 units.
Step 1: Draw all non-red shoes first to maximize failure: Total non-red = 18 (white) + 16 (black) = 34 attempts.
Step 2: Draw red shoes. To delay forming a pair, Raj could draw 10 shoes that all belong to the same foot orientation (e.g., 10 left red shoes) . Attempts added = 10.
Step 3: The very next shoe drawn (34 + 10 + 1 = 45th attempt) is guaranteed to be a right red shoe, completing a matching functional pair . Total maximum attempts = 34 + 10 + 1 = 45.
Answer: (d).
Question details
Year
2023
Paper
CSAT
Question
Q4
Section
Numerical Ability
Sub-topic
Permutations & Combinations (Pigeonhole)
Type
Number theory
Difficulty
Hard
Source hint
Number theory
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