Question

What is the sum of the mean proportional between 2.8 and 17.5 and the third proportional to 8 and 12?

• A. 28
• B. 24
• C. 25
• D. 20

Answer 1

Answer:

C. 25

Solution:

Given:

Numbers =  2.8 and 17.5

Formula used:

(a, b) mean proportional (x) $=\sqrt{ab}$

(a, b) third proportional (y) $=\frac{b^2}{a}$

Calculations:

Mean proportional (x) $=\sqrt{(2.8\times{17.5}}$

$=\sqrt{49}$

⇒ 7 

Third proportional (y) = (12 × 12)/8

⇒ 144/8

⇒ 18

x + y = 18 + 7

⇒ 25

∴ The sum of the mean proportional between 2.8 and 17.5 and the third proportional to 8 and 12 is 25.