A 10 foot rope ladder hangs over the side of a boat with the bottom rung at the surface of the water. There is one foot between rungs and the tide goes up at the rate of 6 inches per hour. How long until three rungs are covered?
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1 hour
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1.5 hour
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2 hour
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None of the above
To solve this question, the user needs to know basic arithmetic, the units of measurement, and the concept of relative motion.
First, we need to determine how many feet are in three rungs of the ladder. We know that the ladder is 10 feet long and there is one foot between each rung, so there are 9 feet of actual ladder. Since there are two spaces between the three rungs, we add 2 feet to the 9 feet of ladder to get a total of 11 feet that need to be covered by the rising tide.
Next, we need to determine how long it will take for the tide to rise 11 feet. Since the tide rises at a rate of 6 inches per hour, or 0.5 feet per hour, we can set up a proportion to solve for the time it will take:
0.5 feet/hour = x hours/11 feet
Solving for x, we get:
x = (11 feet)/(0.5 feet/hour) = 22 hours
Therefore, it will take 22 hours for the tide to rise 11 feet and cover three rungs of the ladder.
Now, let's go through each option and explain why it is right or wrong:
A. 1 hour: This option is incorrect because it is not enough time for the tide to rise 11 feet and cover three rungs of the ladder.
B. 1.5 hours: This option is incorrect because it is not enough time for the tide to rise 11 feet and cover three rungs of the ladder.
C. 2 hours: This option is incorrect because it is not enough time for the tide to rise 11 feet and cover three rungs of the ladder.
D. None of the above: This option is correct. None of the given options is enough time for the tide to rise 11 feet and cover three rungs of the ladder.
The Answer is: D. None of the above.
This is a classic lateral-thinking riddle: the rope ladder hangs from a boat, and boats float — they rise with the tide. So as the tide rises, the boat (and the ladder attached to it) rises right along with the water level, meaning the rungs stay at the same position relative to the waterline forever. No rungs will ever become submerged regardless of how much time passes or how fast the tide rises, since the given rate (6 inches/hour) is a red herring meant to tempt you into a straightforward distance/rate calculation. Hence 'None of the above' is correct — the calculated answer of any fixed number of hours would be wrong because the premise (rungs getting covered) never actually happens.