Find the 17th term of an arithmetic progression. If 15th and 21st term of arithmetic progression is 30.5 and 39.5 respectively.
A38
B35.5
C36
D33.5
Answer:
D. 33.5
Read Explanation:
T15 = a + 14d = 30.5 ------ (1)
T21 = a + 20d = 39.5 ------ (2)
Subtract equation 1 from equation 2
6d = 9
d = 1.5
Put the value of d in equation 1
a + 14 x 1.5 = 30.5
a = 30.5 - 21
a = 9.5
T17 = a + 16d
= 9.5 + 16 x 1.5
= 33.5
