I need help solving this problem

Question

If I start at 2 and count by 3's my 50th number will be... I would like to know if there is a formula that can be used to solve this problem.

Answer 1

If you start at 2, and count by 3s, you get the sequence:

 

2, 5, 8, 11

 

There's a general form for this arithmetic sequence which looks like:

 

a_n = a₁ + d(n - 1)

 

where a_n is the nth term, a₁ is your first term, d is your common difference and n is what term number you're looking for.

 

a₅₀ would equal...

 

a₅₀ = 2 + 3(50-1)

 

a₅₀ = 2 + 3 * 49

 

a₅₀ = 149