Sum of the squares of 3 consecutive odd numbers is 2531. Find how many of these numbers will be prime numbers?

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UGC NET Paper 1: Held on 13th Mar 2023 Shift 1
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Option 3 : 2
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UGC NET Paper 1: Held on 21st August 2024 Shift 1
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Given:

The sum of the squares of 3 consecutive odd numbers is 2531.

Calculation:

According to the given information, the sum of the squares of the three consecutive odd numbers is 2531:

⇒ (2n - 1)2 + (2n + 1)2 + (2n + 3)2  = 2531

Simplifying the equation:

⇒ 4n2 - 4n + 1 + 4n2 + 4n + 1 + 4n2 + 12n + 9 = 2531

⇒ 12n2 + 12n + 11 = 2531

⇒ 12n2 + 12n - 2520 = 0

Dividing both sides of the equation by 12:

⇒ n2 + n - 210 = 0

Now, we can factorize the quadratic equation:

⇒ (n + 15)(n - 14) = 0

So, we have two possible solutions for n: n = -15 and n = 14.

However, n represents an integer, so the valid solution is n = 14.

Now, we can find the three consecutive odd numbers:

First odd number: 2n - 1 = 2(14) - 1 = 27

Second odd number: 2n + 1 = 2(14) + 1 = 29

Third odd number: 2n + 3 = 2(14) + 3 = 31

Now we can check if these numbers are prime:

27 is not prime (divisible by 3 and 9) 29 is prime 31 is prime

Therefore, out of the three consecutive odd numbers, two of them (29 and 31) are prime numbers.

So the answer is 2

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