Final answer:
The explicit rule for an arithmetic sequence is an = a1 + (n-1)d. Using this rule, we can determine that Keena took 15 ballet classes given the total amount she paid and the cost per class.
Step-by-step explanation:
The explicit rule for an arithmetic sequence is given by the formula an = a1 + (n-1)d, where an represents the n-th term of the sequence, a1 is the first term, and d is the common difference between consecutive terms.
For example, if we know that Keena paid a total of $94 to take ballet classes, and if each class costs $6, we can use the explicit rule to find the number of classes. In this case, a1 = 6 and d = 6. Substituting these values, we have:
94 = 6 + (n-1)6
Simplifying the equation, we get 88 = 6(n-1). Solving for n, we find that Keena took a total of 15 classes.
Learn more about Finding the number of classes in an arithmetic sequence