Which explains why the sequence 81, 3, 1/9,... is arithmetic or geometric?

A)The sequence is arithmetic because it decreases by a factor of 1/27
B)The sequence is geometric because it decreases by a factor of 1/27
C)The sequence is arithmetic because it decreases by a factor of 3. THIS ONE
D)The sequence is geometric because it decreases by the factor of 3.

Write an expression to describe a rule for the sequence. Then find the 100th term in the sequence.
3, 10, 17, 24, 31, 38,...
A)n + 7;707
B)7n; 700
C)7n-4; 696 THIS ONE
D)6n-4; 596

The time between a lightning flash and the following thunderclap may be used to estimate, in kilometers, how far away a storm is. How far away is a storm if 12 seconds elapse between the lightning and the thunderclap?
Use the formula d=t/3, where t is the time, in seconds, between the flash and the thunderclap.
A)4 kilometers
B)5 kilometers
C)15 kilometers
D)36 kilometers THIS ONE

2 answers

you got the middle one

take another look at the first and last
81*1/27 = 9
9 * 1/27 = 1/3
http://www.mathsisfun.com/algebra/sequences-sums-geometric.html

3 + 7(n-1) = 3 + 7 n-7 = 7 n - 4 correct
https://www.mathsisfun.com/algebra/sequences-sums-arithmetic.html

NO!!!!
about 330 meters/second for sound in air
d = 330 * 12 = 3960 meters about 4 km