the 6th term of a g.p is 2000 find it's first term of it's common ratio
well, given any a,
ar^5 = 2000
so, r = fifthroot(2000/a)
If you only have one term, it's impossible to find both a and r.
Now, 2000 = 2^4 * 5^3
so, if a = 125/2 and r=2, then ar^5 = 2000