What is the 25th term of the arithmetic sequence where a1=8 and a9=48? answers to choose from. a) 113. b) 118. c) 123. d) 128

First we need to find "d" which is difference between any 2 successive members of the sequence. Because the sequence is arithmetic that means that the difference between any 2 successive members is same and constant.

This is the formula for any member of sequence at position "n"

An = A1 + (n-1) * d

d = (a9 - a1) / (9-1)

d = 5

Now we calculate 25th member:

a25 = a1 + (25-1) * 5

a25 = 128

Answer is d)