Read the word problem. Chan rows at a rate of eight miles per hour in still water. On Wednesday, it takes him three hours to row upstream from his house to the park. He rows back home, and it takes him two hours. What is the speed of the current? Which of the following is a clue that would help solve this word problem?
Answer
A
The entire trip takes five hours.
B
The rate of Chan’s rowing in still water is 8 mph.
C
Chan’s house is next to a river.
D
Chan rows from the house to the park on Wednesday.
Explanation
The speed in still water, 8 mph, is a key clue because the current changes Chan’s speed: upstream, his speed is 8 mph minus the current, and downstream it is 8 mph plus the current. The equal distance each way lets you use the 3-hour and 2-hour travel times to find the current. “The entire trip takes five hours” does not help determine the current by itself.
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