Find the sum of the first 100

terms of the arithmetic

sequence

a1=15 and a 100=307

16100

Step-by-step explanation:

n = 100

a1 = 15

a100 = 307

The first thing you have to do is solve for d

a100 = a1 + (n - 1) * d

307 = 15 + (100 - 1) * d

307 = 15 + 99*d

307 - 15 = 99*d

292 = 99 d

d = 292 / 99

d = 2.94949494

That's a real odd result, but it is what you get.

Sum = (a + L) * n/2

sum = (15 + 307) * n/2

Sum = 322 * 100 / 2

Sum = 16100 It looks like I didn't have to solve for d. The person who made this up sure didn't