Exam Name: NSU Paper Name: Number Series Patterns Fundamentals | NSU Question Status: incorrect Correct Marks: 1 Incorrect Marks: N/A Marks Gained: N/A Total Visit Count: 1 Time Spent: 43.522 seconds Additional Context: I changed my answer 8 times and still got it wrong. What fundamental concept am I missing? ── QUESTION ── Find the next number in the series: 11, 13, 17, 19, 23, ? ── OPTIONS ── A. 25 B. 27 C. 29 D. 31 Correct answer: C My answer: A

Understanding the Problem

You are given the number series:

You chose \(25\), but the correct answer is \(29\).

The fundamental concept you may be missing is this:

This series is made of consecutive prime numbers.

---

Given Data

• Series: \(11,\ 13,\ 17,\ 19,\ 23,\ ?\)
• Options:
  • A. \(25\)
  • B. \(27\)
  • C. \(29\)
  • D. \(31\)

---

Solution Approach

Check whether each number belongs to a special pattern.

Let us see the numbers one by one:

• \(11\) is a prime number
• \(13\) is a prime number
• \(17\) is a prime number
• \(19\) is a prime number
• \(23\) is a prime number

These are not just random numbers. They are prime numbers in order, starting from \(11\).

---

Step-by-Step Solution

---

Why \(29\) Is Correct

The sequence is:

Thus, the correct answer is:

So, Option C is correct.

---

What You Were Probably Thinking

Many students look at the differences:

This gives the pattern:

If you continue that, the next step would be:

That is why \(25\) feels tempting.

But in number series questions, the stronger and more standard pattern is often the intended one. Here, the numbers are clearly consecutive primes, so \(29\) is the best answer.

---

Important Concept to Remember

Prime numbers are numbers greater than \(1\) that have only two factors:

Examples of prime numbers:

Non-prime numbers like \(25\) and \(27\) are composite because they can be divided by other numbers:

---

Quick Exam Tip

1. First, check if the numbers belong to a known set:
   • prime numbers
   • squares
   • cubes
   • multiples
2. Only after that, look at the differences.
3. If two patterns seem possible, choose the more natural and standard one.

---

Final Answer

The next number in the series is:

Correct option: C

---

Key Summary

• The series contains consecutive prime numbers.
• \(25\) is wrong because it is not prime.
• The next prime number after \(23\) is \(29\).

If you want, I can also show you how to quickly spot prime-number series in exams so you do not get trapped by answer choices like \(25\).