Arithmetic sequence question

Question

Violin lesson fees start at $46 per hour in january, 1990, and gradually increased by $2.5 every year. How much is the hourly cost in January of 2014? Hint: it's not a good idea to just apply tn=t1 +d(n-1). How much do you pay in January 1991? 1992? Then use the patter you see.

Answer 1

Any reason given for not following the formula?

 

a_n = a₁ + (n - 1)d

a₁₅ = 46 + (15 - 1)2.5          2014 is the 15th year after 1990

a₁₅ = 46 + (14)2.5

a₁₅ = 46 + 35

a₁₅ = 81

 

In 2014 lessons cost $81.

 

Us the same method to answer the other two questions.