# Find DC

• Jan 15th 2007, 07:51 PM
symmetry
Find DC
To measure the distance (DC) across a pond, a surveyor takes points A and B so that AB is parallel to DC. If AB = 60 feet, EB = 48 feel, and ED = 80 feet, find DC.
• Jan 16th 2007, 04:45 AM
CaptainBlack
Quote:

Originally Posted by symmetry
To measure the distance (DC) across a pond, a surveyor takes points A and B so that AB is parallel to DC. If AB = 60 feet, EB = 48 feel, and ED = 80 feet, find DC.

Where/what is E?

RonL
• Jan 16th 2007, 09:42 AM
Soroban
Hello, symmetry!

Quote:

To measure the distance $DC$ across a pond,
a surveyor takes points $A$ and $B$ so that $AB \parallel DC$.

If $AB = 60\text{ ft},\;EB = 48\text{ ft},\;ED = 80\text{ ft}$, find $DC$.

You forgot to tell us where point $E$ is, but I have a good guess.
Code:

    D * - - - - - - - - - - - - - - - * C             *                      *               80 *              *                         *      *                               *E                             *      * 48                           *              *                       A * - - - - - - - - - - - * B                                   60

From the similar triangles, we have: . $\frac{CD}{80} \:=\:\frac{60}{48}$

Therefore: . $CD \:=\:100\text{ ft}$

• Jan 16th 2007, 10:05 AM
galactus
In real-life, the person helping the surveyor would go to the other side of the pond with a prism and the surveyor would measure the distance with the transit. That's no fun, though. Too easy.
• Jan 16th 2007, 01:21 PM
symmetry
ok
Thank you all, especially soroban. Soroban did a great job with the picture and reply.

Thanks!