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Question

The arithmetic mean of 3, 7, 11, ..., 51 is ______.

This question was previously asked in
RRB NTPC 2025 Under Graduate CBT 1 Question Paper PDF (20-Jun-2026) (Shift 3)
The correct answer is

27

The series 3, 7, 11, ..., 51 is an arithmetic progression with common difference 4.

Number of terms: \(51 = 3+(n-1)\times4 \Rightarrow n-1=12 \Rightarrow n=13\).

For an AP, the arithmetic mean equals half the sum of the first and last terms: \(\dfrac{3+51}{2}=27\).

Hence, the arithmetic mean of the series is 27.

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Similar Questions

  1. If the ratio of the 11th term of an AP to its 18th term is 2 : 3, find the ratio of the sum of its first five terms to the sum of its first 10 terms.
  2. If the sum of five consecutive multiples of 2 is 660, then find the largest number.
  3. The $10^{\text{th}}$ term of the Arithmetic Progression $2, 7, 12, \dots$ is:
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Important Questions from Arithmetic Progression

  1. If the nth term of a sequence is \(\frac{2 n+5}{7}\), then what is the sum of its first 140 terms? 

  2. What is the arithmetic mean of first 8 multiples of 13?

  3. The average of five consecutive odd natural numbers is 27. The product of the first and fifth number is:

  4. Find the sum of all the numbers between 100 to 200 which are divisible by 12.

  5. In a garden, there are 6 daisy plants the first year. Each year, a gardener adds 3 new daisy plants the first year and loses 2 each year. He has 26 jasmine plants the first year and loses 2 each year. When will the number of daisy plants equal the number of jasmine plants after the first year?

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