Question

Find the sum of the arithmetic sequence.

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

240

140

159

35

Answer 1

@ganeshie8

Answer 2

will give best answer & medal!

Answer 3

@hoblos

Answer 4

what is the common difference between the terms ?

Answer 5

2 :)

Answer 6

correct
now we have to find the number of terms n

Answer 7

would that be 5

Answer 8

or 11(counting all the missing terms)

Answer 9

15, 17, 19, 21,23, 25, 27, 29, 31, 33
these are all the terms

Answer 10

whoops, ok got it, what happens next?

Answer 11

33 = 15 + (n-1)*2

you could solve "n" from nth term formula above if u dont wanto guess...

Answer 12

http://www.wolframalpha.com/input/?i=total+%2815%2C+17%2C+19%2C+21%2C+23%2C+25%2C+27%2C+29%2C+31%2C+33%29

Answer 13

@ganeshie8 how do I solve for n

Answer 14

thanku @eliassaab

Answer 15

:)

Answer 16

YW

Answer 17

now we have to right the general form of the sequence
\[\sum_{k=0}^{k=n-1}(a+dk)\]
where a is the first term, and d is common difference

Answer 18

Got it! thank u so much :)