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The sum of 7 consecutive natural numbers is 1617. Find how many of these are prime numbers?

1. 2
2. 3
3. 1
4. 4

7 क्रमागत प्राकृतिक संख्याओं का योग 1617 है। इनमें कितनी अभाज्य संख्याएं हैं?

1. 2
2. 3
3. 1
4. 4
This Question came in
UGC-NET-Hindi-05-March-2023-Shift-2-Q24
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Detailed Explanation & Answer
Given n = 7
Sum till nth term = 1617
d = 1 (consecutive terms have a difference of 1)

Let's assume
First Term = a

Formula to get nth term
nth term = First Term + (n - 1) d
7th Term = a + (7 - 1) x 1
or (6 + a)

Putting it in a formula of total sum
Sum = n (first term + nth term) / 2
1617 = 7(a + a + 6) / 2
or a = 228

Hence, the Seven Numbers are 228, 229, 230, 231, 232, 233, 234
Out of which 2 Numbers 229 and 233 are prime numbers
दिया गया n = 7
nवें पद तक का योग = 1617
d = 1 (क्रमिक पदों का अंतर 1 है)

चलो मान लो
प्रथम पद = a

nवाँ पद प्राप्त करने का सूत्र
nवाँ पद = प्रथम पद + (n - 1) d
7वाँ पद = a + (7 - 1) x 1
या (6 + a)

इसे कुल योग के सूत्र में डालकर
योग = n (पहला पद + nवाँ पद) / 2
1617 = 7(a + a + 6) / 2
या a = 228

अतः, सात संख्याएँ 228, 229, 230, 231, 232, 233, 234 हैं
जिनमें से 2 संख्याएँ 229 और 233 अभाज्य संख्याएँ हैं
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