Let length of side of smaller square = a
Then length of side of bigger square = 1.5a
Area of smaller square = a2
Area of bigger square = (1.5)2a2 = 2.25a2.
Probability that dart will land in the interior of the smaller square = (Area of smaller square)/(Area of bigger square) = a2/2.25a2 = 1/2.25
∵ Geometrical probability,
P(E) = (measure of specified region part)/(measure of the whole region)