Free Practice Question
PS · Problem Solving
sub-505
Combinations
Emily is creating 3-letter combinations using 26 letters of the alphabet, where the middle letter must be a vowel, and both the first and third letters must be different consonants. How many unique combinations can she create?
Answer Choices
Correct answer marked belowA
1,800
B
1,900
C
2,000
2,100
Correct
E
2,300
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Explanation
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Official Explanation
Official
Let's denote the code as ABC. There are 5 vowels: a, e, i, o, u, which can occupy position B. Thus, there are 5 choices for B. For position A, we can choose any of the 21 consonants. Since A and C must be different and…
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Comments
2
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A
AlejandroFeb 15, 2025
thank you taking time to upload it!
N
NiharikaJan 2, 2025
thanks a lot
What this question tests
What it tests
Whether you can count arrangements and selections correctly — permutations vs. combinations.
Common trap
Overcounting: treating a selection as ordered when order does not matter, or forgetting to divide by duplicates.
Details
Difficulty
sub-505
Type
PS
Category