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45 vote

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

Asked on by | Votes 45 | Views: 3604 | Tags: ratio and proportion     | quantitative aptitude     | Add Bounty

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


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2 answers

40 vote
Answered by on | Votes 40 |

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.
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26 vote
Answered by on | Votes 26 |

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