Arithmetic progression (nth term): Find the 21st term of 3, 9, 15, ... Sequence parameters: first term a = 3; common difference d = 6. Compute t(21) using the AP formula. Choose the correct value.
Verbal Reasoning
Series Completion
Difficulty: Easy
Choose an option
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A117
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B121
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C123
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D129
Answer
Correct Answer: 123
Explanation
Givena = 3, d = 6, n = 21
Formulat(n) = a + (n−1)d
Step-by-step calculationt(21) = 3 + 20×6 = 3 + 120 = 123
VerificationTerms grow: 3, 9, 15, ... adding 6 each time; 21st fits 123.