Q2 of 59 Page 77

If (28 - x) is the mean proportional of (23 - x) and (19 - x) then find the value of x.

A number b is said to be mean proportional of two numbers a and c if


b2 = ac.


∴ From the definition of mean proportion, we get:


(28 - x)2 = (23 - x)(19 - x)


⇒ 784 + x2 – 56x = 437 - 42x + x2


⇒-56x + 42x = 437 – 784


⇒ -14x= -347


⇒ x = 347/14


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