A) 2.8
B) 4.16
C) 4.8
D) 2.16
Correct Answer: B
Solution :
By hypothesis, \[\sqrt{ab}=8\] or \[ab=64\] ??(i) Now \[\frac{2ab}{a+b}=6.4\] From equation (i) \[2\times 64=6.4\,(a+b)\] or \[a+b=20\] ??(ii) or \[b=20-a\] Substituting the value of b in equation (i), we get \[a(20-a)=64\] or \[{{a}^{2}}-20a+64=0\] or \[(a-16)\,(a-4)=0\] \[\therefore \] \[{{a}^{2}}=16\] or \[a=4\] From equation (ii) \[b=20-16\] or \[20-4=4\] or \[16\] Hence the numbers are \[4,16\].
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