10. One hundred rectangles are arranged edge-to-edge in a continuation of the pattern shown. Each rectangle measures $3 \mathrm{~cm}$ by $1 \mathrm{~cm}$. What is the perimeter, in $\mathrm{cm}$, of the completed shape?
A 800
B 700
С 602
D 600
E 502
10. C The perimeter of each rectangle is $2 \times(3+1) \mathrm{cm}=8 \mathrm{~cm}$.
The total perimeter, in $\mathrm{cm}$, of the separate rectangles is therefore $100 \times 8=800$. When two rectangles are placed together at a "join" in the pattern, there is an overlap of length $1 \mathrm{~cm}$ and the total perimeter is reduced by $2 \mathrm{~cm}$. In the complete pattern there are 99 joins and hence its perimeter, in cm, is $800-99 \times 2=800-198=602$.