Answer:
The partial sum is 561
Explanation:
Given:
The arithmetic series = 9+12+15...+51+54+57
Partial sum between 9 and 57, with d=3
To Find :
The partial sum = ?
Solution
The given series is a arithmetic series with difference 3.
So the series is
9,12,15,18,21,24,27,30,33,36,29,42,45,48,52,51,54,57
Thus There are 17 terms,
Here the is a middle term is the the ninth,
The 9 term is




Now the
The partial sum is 33 x 17 = 561