The yellow square that surrounds most of

$513000mE$

$514000mE$

the map in Fig. A$1\mathrm{.}3\mathrm{.}1$ represents a horizon$-$

Figure A$1\mathrm{.}3\mathrm{.}1$

tal area on the ground that is $1km$ by $1km$ in dimension, so we can use a side of that square as a bar scale.

$($a$)$ As accurately as you can, measure the length of a side of this square in $cm$; we'll use the variable name $a5$ for this length. $a5=,cm$

$($b$)$ We will use the variable name $b5$ for the number of $cm$ in $1km.b5=,cm$

$($c$)$ The fractional scale of this map can be found by dividing $b5$ by $a5-$we'll call that result $e5.$ The fractional scale is $1/$e$5,$ or $1$:e$5.1/$ or $1$ That means that $1$ length unit of any sort $(cm,$ for example$)$ on the map represents $e5$ length units of the same sort $(cm)$ on the ground.