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UGC-NET-Paper1

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The sum of all even natural numbers between 1 and 81 is

(1) 3280
(2) 3321
(3) 1646
(4) 1640

1 और 81 के बीच की सभी सम प्राकृत संख्याओं का योग है

(1) 3280
(2) 3321
(3) 1646
(4) 1640
This Question came in
UGC-NET-20-June-2019-Shift-2-Q22
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Detailed Explanation & Answer
The even numbers between 1 and 81 would be: 2, 4, 6, ..., 80.

Hence,
First Term = 2
Last Term = 80
Common Difference = 2
n = ?

By putting the above values in the formula to get the Last Term:
Last Term = First Term + (n - 1) x d
80 = 2 + (n - 1) x 2
By solving the equation: n = 40

The sum of all even numbers:
Sum = n (First Term + Last Term) / 2
= 40 (2 + 80) / 2
= 1640
1 और 81 के बीच सम संख्याएँ होंगी: 2, 4, 6, ..., 80।

इस तरह,
प्रथम पद = 2
अंतिम पद = 80
सामान्य अंतर = 2
एन = ?

अंतिम पद प्राप्त करने के लिए उपरोक्त मानों को सूत्र में डालकर:
अंतिम पद = पहला पद + (एन - 1) x डी
80 = 2 + (एन - 1) x 2
समीकरण को हल करके: n = 40

सभी सम संख्याओं का योग:
योग = n (प्रथम पद + अंतिम पद) / 2
= 40 (2 + 80) / 2
= 1640
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