Question

two objects of masses in the ratio 1:2. a what is the ratio of their kinetic energies

Answer 1

Ke = $mv^2/2$
$Ke _{1} = 1x *v^2/2$  -- taking mass as 1x
$K e_{2} = 2x * v^2/2$   -- taking mass as 2x
ratio == 

$(1x * v^2/2)/(2x * v^2/2)$
which gives us 
$1/2$
or 

1:2