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Common Terminology

Question 15 I...

Question

Question 15
If the first term of an AP is –5 and the common difference is 2, then the sum of the first 6 terms is

A) 0
B) 5
C) 6
D) 15

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Solution

Given:
a = - 5
d = 2
$∴ S_{6} = \frac{6}{2} [2 a + (6 - 1) d] [∵ S_{n} = \frac{n}{2} {2 a + (n - 1) d}]$
$= 3 [2 (- 5) + 5 (2)] = 3 (- 10 + 10) = 0$

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Similar questions

Q. Question 15
If the first term of an AP is –5 and the common difference is 2, then the sum of the first 6 terms is

A) 0
B) 5
C) 6
D) 15

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Q. Question 33
The sum of the first n terms of an AP whose first term is 8 and the common difference is 20 is equal to the sum of first 2n terms of another AP whose first term is –30 and the common difference is 8. Find n.

If $9^{t h}$ term of an AP is 15 and the common difference is 2, then the first term of the AP is

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Common Terminology

Standard X Mathematics

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