Aptitude - Numbers - Discussion
Discussion Forum : Numbers - General Questions (Q.No. 116)
116.
The sum of first 45 natural numbers is:
Answer: Option
Explanation:
Let Sn = (1 + 2 + 3 + ... + 45)
This is an A.P. in which a = 1, d = 1, n = 45 and l = 45
 Sn = |
n | (a + l) | = | 45 | x (1 + 45) = (45 x 23) = 1035 |
| 2 | 2 |
Required sum = 1035.
Discussion:
3 comments Page 1 of 1.
Lokeshwar said:
7 years ago
N = 45 then formula for "n" natural numbers is (n(n+1))/2.
So, (45(45+1))/2 = 1035.
So, (45(45+1))/2 = 1035.
(3)
Durga said:
8 years ago
Formula.
s45=n(n+1)/2.
s45=45(45+1)/2,
=45(46)/2,
=45(23),
=1035.
s45=n(n+1)/2.
s45=45(45+1)/2,
=45(46)/2,
=45(23),
=1035.
(2)
Suresh said:
1 decade ago
In general, ((first term)+(last term))*(half the number of terms).
(1)
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