Four equal circles, each of radius a units, touch each other.

When four circles touch each other, their centres form the vertices of a square. The sides of the square are 2a units.

Area of the square $=(2 a)^{2}=4 a^{2}$ sq. units

Area occupied by the four sectors

$=4 \times \frac{90}{260} \times \pi \times a^{2}$

$=\pi a^{2}$ sq. units

Area between the circles = Area of the square -">− Area of the four sectors

$=\left(4-\frac{22}{7}\right) a^{2}$

$=\frac{6}{7} a^{2}$ sq. units