Find the sum of the arithmetic sequence.

15, 17, 19, 21, ..., 33

Question

Find the sum of the arithmetic sequence.

15, 17, 19, 21, ..., 33

anonymous · Answer

So just do 15+17+19+21 all the way to 33, it's going up my 2 numbers each time.

anonymous · Answer

240 ! Thank You.

anonymous · Answer

any idea how???

john_es · Answer

You also can use the Gauss' trick,
$$\frac{(15+33)10}{2}=240$$

john_es · Answer

10 is the number of odd numbers you add between 15 and 33, both included.

anonymous · Answer

initial Input segment value as 15......
Internal common difference as 2....
final Output assigned value as 33
and get the resultant output!!

anonymous · Answer

xJakester...poor method. And what if I wanted 13 + 15 + 17 + 19 + ......+ 23,117? Are you gonna sit and type all these numbers for a few hours? Correct method is to use the formula for the SUM of an arithmetic series.

anonymous · Answer

First find out the number of terms in the series. Apply the forum 
$$Tn = a + (n-1)d$$
a = 15, i.e. the first term
Tn = nth term, which in this case is 33
d = difference between successive terms = 17-15 = 2
Therefore, 33 = 15 + (n-1) * 2, which gives n = 10
Now apply the formula for the sum of n numbers in an AP
$$S = \frac{ n }{ 2 } (2a + (n-1)d)$$
This gives you the solution S = 240 (where n = 10)

anonymous · Answer

I do thank you all for your time, as well as acquiring me with numerous ways to solve this problem :)

anonymous · Answer

give me a medal..........M waiting

anonymous · Answer

Jus kiddie........lol