Question

there are 13 left - handed and 21 right - handed spirals on the cacti in the photograph. what is special about these numbers? a. the value of the 13th term of the pyramidal sequence is 21. b. the value of the 13th term of the fibonacci sequence is 21. c. they are consecutive terms in the fibonacci sequence. d. they are consecutive terms in the pyramidal sequence.

Explanation:

First, recall the Fibonacci sequence: it starts with 0, 1, and each subsequent term is the sum of the two preceding ones, so the sequence goes 0, 1, 1, 2, 3, 5, 8, 13, 21, ... Here, 13 and 21 follow each other directly in this sequence. Pyramidal sequences involve sums of squares or cubes, which do not include these as consecutive terms, and the 13th term of the Fibonacci sequence is not 21 (the 8th term is 13, 9th is 21).

Answer:

C. They are consecutive terms in the Fibonacci sequence.