8. Two identical rulers are placed together, as shown (not to scale).
Each ruler is exactly $10 \mathrm{~cm}$ long and is marked in centimetres from 0 to 10 . The $3 \mathrm{~cm}$ mark on each ruler is aligned with the $4 \mathrm{~cm}$ mark on the other.
The overall length is $L \mathrm{~cm}$. What is the value of $L$ ?
A 13
B 14
C 15
D 16
E $\quad 17$
Solution: $\mathbf{A}$
The distance between the $4 \mathrm{~cm}$ mark and the $10 \mathrm{~cm}$ mark at the end of the ruler is $(10-4) \mathrm{cm}=6 \mathrm{~cm}$. The overall length is made up of the length on each ruler from the $4 \mathrm{~cm}$ mark to the $10 \mathrm{~cm}$ mark, plus the length from the $3 \mathrm{~cm}$ mark to the $4 \mathrm{~cm}$ mark. This latter distance is $1 \mathrm{~cm}$. So, $L=6+6+1=13$.