70) Which of the following best describes the series 100 A) arithmetic; \( a=3, d=5 \) B) arithmetic; \( a=5, d=3 \) C) geometric; \( a=3, r=5 \) D) geometric; \( a=5, r=3 \)

The series you're looking at appears to be a bit mysterious since the details of its construction aren't laid out clearly! If we're assuming that "100" is a keyword or an output of some series you'd expect to generate (like needing to define 'n' terms), it’s crucial to tackle the definitions first. Arithmetic series add a constant (the common difference) with each term, while geometric series multiply by a constant (the common ratio). For a clear solution, you'd want to establish whether we’re summing or multiplying to reach 100. Clue: if it’s the addition of each term to reach 100 starting from 3 or 5, you'll find the appropriate arithmetic series definition more handy than the geometric one. Now, when presented with these options, make sure to test the arithmetic series options because they offer a more straightforward trajectory toward a specific number like "100." If you’re diving deeper into sums, consider exploring how formulas for the sum of finite arithmetic or geometric series can uncover hidden terms and help you bridge gaps to numbers like 100. This foundational knowledge can be a fun ride through the realms of mathematics!