Aptitude - Numbers - Discussion

Discussion Forum : Numbers - General Questions (Q.No. 57)

Numbers

57.

	1 -	1		+		1 -	2		+		1 -	3		+ ... up to n terms = ?
		n					n					n

1	n
2

1	(n - 1)
2

1	n(n - 1)
2

None of these

Answer: Option

Explanation:

Given sum

= (1 + 1 + 1 + ... to n terms)	-		1	+	2	+	3	+ ... to n terms
			n		n		n

= n -	n		1	+ 1		[ Ref: nth terms = (n/n) = 1]
	2		n

= n -	n + 1
	2

=	1	(n - 1)
	2

Discussion:

15 comments Page 2 of 2.

Gowry said: 7 years ago

Can anyone explain clearly? Please.

MADHU. said: 5 years ago

Please kindly tell me how to find 9it? Anyone explain to me, please.

Sujata said: 4 years ago

Please anyone explain me, I can't understand.

(3)

Kelbin said: 4 years ago

=1+2+3+.........+n=n(n+1)/2.

= n-1/n(1+2+3+....+n)
= n-1/n *n(n+1)/2,
= n-(n+1)/2,
= 2n-n-1/2,
= n-1/2.
= 1/2(n-1).

(8)

Shreya said: 3 years ago

I am not understanding it. Please, anyone, help me to get this.

(4)

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