geometric progressions

[irelandscall]

insert 4 geometric means between 200 rpm and 1200 rpm.

[Fibonacci]

A geometric progression is one on which each term is multiplied by a constant value to get the next term
General form of a G. P.: a, ar, ar^2, ar^3, ...
To insert 4 geometric means between the two given numbers is to form a geometric progression of 6 (4+2)) terms having the two given numbers as the first and last terms

The first term of your progression (a) = 200 and the sixth term (ar^5) =1200
so ar^5 / a = r^5 = 1200/200= 6
so now you know r^5 is 6

now solve the equation r^5 = 6 and you have found the constant value and can then find the missing terms by multiplying each term starting from 200 by this result.

( n.b. ^ is an accepted way of typing to the power of)