Help with direct variations
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Given:
First term of an arithmetic sequence is 2.
Sum of first 15 terms = 292.5
To find:
The common difference.
Solution:
We have,
First term:
Sum of first 15 terms:
The formula of sum of first n terms of an AP is
Where, a is first term and d is common difference.
Putting , n=15 and a=2 in the above formula, we get
Divide both sides by 15.
Dividing both sides by 7, we get
Therefore, the common difference is 2.5.