Thread: River problem

A "cute" li'l problem:

A river is 1000 ft. wide and 10 ft. deep. It travels at 4 mph.
How long will it take to discharge a cubic mile of water into the ocean.

$\dfrac{1000}{5280}\times \dfrac{10}{5280} \times 4 = \dfrac{25}{17424}~mile^3/hr=\text{discharge rate in cubic miles per hour}$

so it takes

$\dfrac{17424}{25}~hr \text{ to discharge a cubic mile}$

$\text{that's 29 days}$

Merci Monsieur Romsek; much "shorter" than mine:

4 mph = 352 fpm

1 feet = 1 * 10 * 1000 = 10000 cu ft
352 fpm = 3520000 cu ft

1 cu mile = ~ 147,200,000,000 cu ft
147200000000 / 3520000 = 41818 min = 697 hrs

697 / 24 = 29 days.