Final answer:
By using the formula for the nth term of a geometric sequence, it is determined that Nina and Zoe sold 243 cookies on Friday, following a pattern where sales tripled each day.
Step-by-step explanation:
The student's question involves finding how many cookies was sold on a specific day given a geometric sequence pattern of cookie sales. The cookie sales started with 3 on Monday and increased by a factor each day. A geometric sequence is defined by its initial term and a common ratio, which in this case is 3, since the cookie sales are tripling each day. Monday is considered the first day of the sequence.
- To figure out the number of cookies sold on Friday, we need to identify Friday as the fifth day in the sequence.
- Next, we use the formula for the nth term of a geometric sequence, which is Tn = a * r^(n-1), where 'a' is the first term, 'r' is the common ratio, and 'n' is the term number.
- For our sequence: a=3, r=3, and n=5 for Friday.
- The number of cookies sold on Friday is T5 = 3 * 3^(5-1) = 3 * 3^4 = 3 * 81 = 243 cookies.
Nina and Zoe sold 243 cookies on Friday.