makhdoom ghaya
asked
in Quantitative Aptitude
Oct 28, 2017

1,281 views
1 vote

Best answer

We know :

a) Harmonic mean of two positive numbers a and b = 2ab/(a + b)

b) Geometric mean of two positive numbers a and b = √ab

So given , H.M. / G.M. = 12 / 13

==> [2ab / (a+b)] / √ab = 12 / 13

==> √ab / (a+b) = 6 / 13

==> ab / (a+b)^{2} = 36 / 169

==> a = 4k and b = 9k

**Hence the ratio a : b = 4 : 9**

**Hence C) should be the correct option.**