7. The diagram shows a rectangle of size $7 \mathrm{~cm} \times 11 \mathrm{~cm}$ containing two circles that each touch three of the sides of the rectangle. What is the distance between the centres of the two circles?
A $2 \mathrm{~cm}$
B $2.5 \mathrm{~cm}$
C $3 \mathrm{~cm}$
D $3.5 \mathrm{~cm}$
E $4 \mathrm{~cm}$
7. $\mathbf{E}$ From the diagram, it can be seen that the distance between the centres of the two circles is $11 \mathrm{~cm}-2 \times$ the radius of a circle or equivalently $11 \mathrm{~cm}$ - the diameter of each circle. Since this diameter is $7 \mathrm{~cm}$, the distance between the centres is $11 \mathrm{~cm}-7 \mathrm{~cm}=4 \mathrm{~cm}$.