Question

Mean proportional between 9 and a number is 19.Find the number and third proportional to them.

Answer 1

Let the desired value be x.
By the question,
$\frac{9}{ x} = \frac{x}{19} \\ or \: {x}^{2} = 19 \times 9 \\ or \: x = \sqrt{19 \times 9 } = \sqrt{171} = 13.08(approx.)$

Answer 2

Answer:

Definition of Continued Proportion: ... i.e. in a : b = b : c; b is the mean proportional between a and c. The third quantity is called the third proportional to the first and the second. i.e. in a : b = b : c; c is the third proportional to a and b. For example, let us consider the numbers 6, 12, 24.

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