Free Practice Question
PS · Problem Solving
sub-505
Sequences
In a neighborhood, there are several houses with doorplate numbers that are all odd. The first doorplate number is 123 and the last one is 273. How many houses are there?
Answer Choices
Correct answer marked below76
Correct
B
81
C
91
D
101
E
111
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Explanation
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Official Explanation
Official
The sequence of doorplate numbers starts at 123 and ends at 273, including both endpoints. The odd numbers in this range are 123, 125, 127, ..., 273. To find the total count of these odd numbers, we calculate it as follows: the difference…
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Comments
2
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C
CoverApr 8, 2024
Great!
O
OshankMar 21, 2025
pls explain more?
What this question tests
What it tests
Your ability to spot and extend arithmetic and geometric sequences and work with recursive definitions.
Common trap
Off-by-one errors in indexing (a₀ vs a₁) or confusing an arithmetic difference with a geometric ratio.
Details
Difficulty
sub-505
Type
PS
Category