What is the common difference of a 43-term arithmetic sequence where the first term is -13 and the sum is 9,374?

11
11.5
12
12.5

Question

What is the common difference of a 43-term arithmetic sequence where the first term is -13 and the sum is 9,374?
 	
	11
	11.5
	12
	12.5

anonymous · Answer

do you have any formulas?
look them up in wiki

anonymous · Answer

http://www.mathwords.com/a/arithmetic_sequence.htm

anonymous · Answer

The first term is a1, the common difference is d, and the number of terms is n.

an = a1 + (n – 1)d

plug in
9374= -13+ (43 – 1)d   solve for d

anonymous · Answer

223.5? whatttt

anonymous · Answer

http://www.mathwords.com/a/arithmetic_series.htm here another formula

anonymous · Answer

use the series not sequence lol

campbell_st · Answer

well i think you have made a error.... 

the sum of an arithmetic series is 

$$S_{n} = \frac{n}{2}[2a + (n -1)d]$$

use the information to solve for d

$$9374 = \frac{43}{2}[2 \times -13 + (43 -1)d]$$

the formula shown by @timo86m is for calculating a term in an arithmetic sequence

anonymous · Answer

9374 = 43/2*(2*(-13)+(43-1)*d)
d=11

anonymous · Answer

Thank you both., I had the equation going ahhaa

anonymous · Answer

Might I ask one more?

anonymous · Answer

well i am going to bed :( sorry

anonymous · Answer

Oh okay.