Three number are in continued proportion,whose mean proportional us 12 and the sum of the remeanining two numbers is 26,the find these numbers.
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Given :-
- Three numbers a, b, c are in continued proportion whose mean proportion is 12 and sum of other two numbers (a and c) be 26.
To find :-
- The numbers a, b, c.
Solution:-
Let the numbers be a, b, c so that they are in continued proportion.
So b is called mean proportion between 'a' and 'c'.
Since, mean proportion is 12
=> b = 12
Now, according to statement,
a + c = 26
=> c = 26 - a ....(1)
Since a, b, c are in continued proportion,
=> b² = ac
=> 12² = a × (26 - a) [using (1) and b = 12]
=> 144 = 26a - a²
=> a² - 26a + 144 = 0
=> a² - 18a - 8a + 144 = 0
=> a(a - 18) - 8(a - 18) = 0
=> (a - 18)(a - 8) = 0
=> a = 18 or 8
So, when a = 8 => c = 18
and when a = 18 => c = 8
So numbers are 8, 12 and 18 or 18, 12 and 8.
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