The fifth term of an arithmetic sequence is 18, and the sum of the first 32 terms is 1448. Find the ninth term.
+20 Sum of arithmetic sequence
Sum32 = n/2 ( 2a1 + (n-1)d)
= 32/2 (2a1 + (32-1)d)
1448 = 16 (2a1 + 31d)
5th term = 18 = a1 + 4d so a1 = 18- 4d use this value of a1 in the red equation above to calculate 'd'
then ninth term will be: 5th term + 4d = 18 + 4(d)
