Question

If √6 is the geometric mean between 4 and another number, then the number is
1.5
9
24

Answer 1

1.5

Answer 2

√(4*x) = √6
where x represents the unknown number.
Now, solve for the unknown number x but taking the square of each side of the equal sign to get rid of the square root sign:
[√(4*x)]^2 = [√6]^2
4*x = 6
Solve for x:
x = 6/4
x = 3/2

3/2 = 1.5