Question

The first term of a geometric sequence is 40. The third term is 2.5, what is the second term ? (10,12,16,20)

Answer 1

the 2nd term will be the geometric mean between the 1st and 3rd.
can u find the geometric mean ?

Answer 2

hint: the geometric mean between a and b is \(\sqrt{ab}\)

Answer 3

how to solve without memorizing anything:

the first term is 40

so 40r would be the second term

then 40r^2 would be the third term

so you have \[40r^2 = 2.5\]
solve for r. Then, you can solve for second term by multiplying r to 40

Answer 4

R is 0.06