Question

Find the 17th term of an arithmetic progression. If 15th and 21st term of arithmetic progression is 30.5 and 39.5 respectively.

• A. 38
• B. 35.5
• C. 36
• D. 33.5

Answer 1

Answer:

D. 33.5

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