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Find two numbers such that their mean proportional is 18 and the third proportional to them is 144.

Find two numbers such that their mean proportional is 18 and the third proportional to them is 144.
1). 6 and 42
2). 9 and 36
3). 3 and 18
4). 6 and 12

This Question has 2 answers.

Let the numbers are x and y,

Mean proportional = √xy = 18

⇒ xy = 324      ---- (1)

Third proportional = y2/x = 144

⇒ y2 = 144x     ---- (2)

Putting the value of x from this in 1st equation,

⇒ y3/144 = 324

⇒ y3 = 324 × 144

⇒ y3 = 18 × 18 × 18 × 8

⇒ y = 18 × 2

⇒ y = 36 and x = 324/36 = 9

∴ Two numbers are 9 and 36.

Hi friends, it's answer is 9 and 36. Surely!!!!

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