The mean proportional between 9 and 16 is
(a) 12.5
(b) 12
(c) 5
(d) none of these
Given numbers are 9 and 16.
We know that, if a:b::c:d then ad=bc
i.e., Product of extremes = Product of the means.
Suppose that the mean proportional is x
Then, 9:x::x:16
⇒9×16=x×x
⇒144=x2
⇒√144=x
⇒12=x
Hence, Option (c) is correct.
(or)
Note: The mean proportional between a and b is √ab.
⇒ The mean proportional between 9 and 16 is
=√16×9=√144=12