About Soroban Expertise I have a systematic and orderly way to organize the facts in a word problem, which (usually) leads clearly to the necessary equation. I think I can help with all types of word problems.
Experience 38 years of teaching college-level math, mostly at a two-year college.
Education/Credentials BS and MS in mathematics, SUNY Albany
Expert: Soroban Date: 2/16/2008 Subject: rate of speed in water
Question A speedboat takes 1 hour longer to go 24
miles up a river than to return. If the boat cruises at 10
miles per hour in still water, what is the rate of the current?
Answer Hello, Melissa!
Here's my approach to upstream-downstream problems . . .
We'll use: [Distance] = [Speed] x [Time]
and its variation: T = D/S
Let x = rate of the current (in miles per hour).
Going against the current, the boat's speed is reduced.
Its speed is: (10 - x) mph.
To go 24 miles, it takes: 24/(10-x) hours.
Going with the current, the boat's speed in increased.
Its speed is: (10 + x) mph.
To go 24 miles, it takes: 24/(10+x) hours.
Going upstream takes one hour longer than downstream.
