Win tickets to a Tina Turner concert if when you're rolling

down a river you can solve the WSU Math Department's

MEASURING

THE RIVER

A traveller reaches a river at the
point A, and wishes to know the width across to B. As he has no means of
crossing the river, what is the easiest way of finding it's width?

Solution:

Measure any convenient distance
along the bank from A to C, say 40 yards. Then measure any distance perpendicularly
to D, say 12 yards. Now sight along along DB and find the point E. You
can then measure the distance from A to E, which will here be 24
yards, and from E to C, which will be 16 yards. Now AB:DC = AE:EC, from
which it is evident that AB, the width of the river, must be 18 yards.