Question 914497
If the side lengths of the smaller and larger squares are {{{s}}} and {{{S}}} respectively,
the perimeters are {{{4*s}}} and {{{4*S}}} respectively,
with {{{4*S=73.5}}}
The ratio of their sides and perimeters is {{{s/S=4*s/4S}}} ,
and the ratio of their areas is {{{s^2/S^2}}} .
We know that {{{s^2/S^2=6/7}}} .
{{{s^2/S^2=6/7}}}-->{{{(s/S)^2=6/7}}}-->{{{4*s/4S=sqrt(6/7)}}}-->{{{4*s=sqrt(6/7)*(4*S)}}}
So, {{{4*s=sqrt(6/7)*73.5}}}--->{{{4*s=highlight(68.0)}}} (rounded).


NOTES:
In general, when you have similar shapes (same figure, or 3-D solid, but scaled up or down),
if the ratio of length measures (side lengths, perimeters, circumferences, etc) is {{{R}}},
then the ratio of the corresponding areas is {{{R^2}}} ,
and (if the similar shapes are 3-dimensional) the ratio of the volumes is {{{R^3}}} .
The larger square is a scaled up version of the smaller square, so that applies.
(We could not say the same of triangles, or rectangles).