Question

Find the 15th term in the following arithmetic sequence
1, 6, 11, 16, ...

Answer 1

Explanation:

21,26

26 is the answer

Answer 2

15th term is 71

Explanation:

Explicit Rule for arithmetic sequence is: Tn = a + (n - 1)*(d), where a is the first term and d is the common difference

The first term is 1, hence a = 1

The common difference is 5 (6 - 1 = 5, 11 - 6 = 5...), hence d = 5

Tn = 1 + (n - 1)*(5)

We are trying to find the 15th number.

T₁₅ = 1 + (15 - 1)*(5)

= 1 + (14)*(5)

= 1 + 70

= 71