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mean proportional[′mēn prə′pȯr·shən·əl]
For two numbers a and b, a number x, such that x / a = b / x.
A mean proportional between two positive numbers is a number equal to the square root of their product. Thus, if a:x = x:b, then x is a mean proportional between a and b, and . The mean proportional x is also called the geometric mean of a and b.