The mean proportion between 4 and 64 is :

The correct answer is Option (2) → 16

The mean proportional between \(a\) and \(b\) is the number \(x\) with \(a:x=x:b\), so \(x^2=ab\) and \(x=\sqrt{ab}\).

• \(x=\sqrt{4\times64}=\sqrt{256}=16\)