Question

5th term of an arithmetic sequence is 15 and its 9th term is 27 .
a) What is its common difference ?

Answer 1

Step-by-step explanation:

Given ,

a(5) = 15

a(9) = 27

We know,

a(n) = a1 + (n-1)d

thus,

a(5) = a1 + 4d = 15 ------ 1

a(9) = a1 + 8d = 27 ------ 2

Applying elemination method on equation 1 and 2,

we get,

4d = 12

=> d = 3