New Enroll in RBI Grade B New Batch - Starts on May 21

    Question

    The number of terms in the sequence 5, 20, 80,

    320,……………., 5120 is:
    A 9 Correct Answer Incorrect Answer
    B 7 Correct Answer Incorrect Answer
    C 6 Correct Answer Incorrect Answer
    D 8 Correct Answer Incorrect Answer

    Solution

    The given sequence is 5, 20, 80, 320, ………., 5120 We can see that, the given series is a geometric progression with common ratio 4. nth term of a geometric progression is given as: ar(n-1) Where, a = first term, r = common ratio ∴ 5 × 4(n-1) = 5120 ⇒ 4(n-1)= 5120/5 = 1024 ⇒ n – 1 = 5 ⇒ n = 6

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