Question

What is the sum of the finite arithmetic series (-5)+0+5+10+ ......+65

a. 900
b. 455
c. 450
d. 445

Answer 1

If you want to solve this problem using formulas, there are two important formulas:

t1 = first term = -5

tn = nth term = last term = -5

n = numbr of terms

Sn = sum of the n terms

tn = t1 + (n - 1)d ---> 65 = -5 + (n - 1)(5)

65 = -5 + 5n - 5

65 = -10 + 5n

75 = 5n

n = 15

Sn = n(t1 + tn)/2 ---> Sn = 15(-5 + 65)/2

Sn = 450

So ur answer rounds up to 450

Letter c

:)

hope i helped

~Luis