The SeaCare corporation is developing a new emergency inflatable raft

A is out for unrelated information
B we are not concerned about the ease of climbing into the raft from water .It may true but we are just interested in whether the raft can hold 1500 lbs in relatively calm water.
D so we are gain not concerned about how the weight is distributed on the raft .
E Out of scope

The official answer is C but still i am unable to relate C with the argument
Hi mikemcgarry
Please explain the logic behind the choice .

A is out for unrelated information
B we are not concerned about the ease of climbing into the raft from water .It may true but we are just interested in whether the raft can hold 1500 lbs in relatively calm water.
D so we are gain not concerned about how the weight is distributed on the raft .
E Out of scope



I'm the author of this question and I'm happy to respond.

It's important to understand all the words in the prompt--if there's a term that appears in the prompt that you don't know, you really have to understand its precise definition and all its implications.

Here, one critical word is "buoyancy." Superficially, it means "ability to float." Another that appears in choice (C) is "density." This is "the ratio of the mass of an object to the total volume of an object."

Think about what those definitions imply. A substance of very low density, such as styrofoam, would float, while a substance of very high density, such as a solid block of iron, would not float--it would sink immediately. In other words, density has something to do with buoyancy, with whether something floats. That's the general idea of why there's a connection between (C) and the argument.

To understand more precisely, you have to have a basic understanding of physical science--in the US, these mostly likely would be facts taught in middle school (grades 7-8). The density of water is around 1 gram/(cm^3)--in fact, historically, that was the original motivation for the definition of the "gram." If an object has a density greater than the density of water, the object sinks in water; conversely, if an object has a density less than the density of water, the object floats in water--that is to say, it is buoyant. More generally, an object is buoyant in a fluid floats and is buoyant in that fluid if the density of the object is less than the density of the fluid. For example, a solid block of iron will sink in water, but it will float in a vat of mercury, the liquid metal that is even more dense than iron.

Now, let's take this understand back to the CR argument.
(C) these beta tests were conducted in fresh water which is less dense than salt water.
For illustration purposes, let's make up imaginary numbers. Let's say that fresh water has a density of 1.00, and let's pretend that salt water has a density of 1.10. Well, if the raft floated in fresh water, it had to have a density less than 1.00. Any number less than 1.00 is definitely less than 1.10!! (Mathematically, that property is called "transitivity of inequality": if M < N and N < P, then we know M < P.) Therefore, buoyancy in freshwater would be a strong guarantee of buoyancy in salt water. This is why (C) strengthens the argument.

Further real-life connections to (C): I don't know whether you have noticed that it's slightly easier to float and bob in ocean water than it is in, say, a fresh water river or lake. The on the Israel/Jordan border has a particularly high salt content, so much that nothing can live in that water, and correspondingly, a particularly high density, which makes floating almost effortless.

For the GMAT CR, you don't need an expert level of knowledge, but you need to have a familiarity with what I would call the basic facts of the world: basic physical science, basic economics, basic facts about world's political & judicial systems, etc. etc. See:

Does all this make sense?
Mike

A is out for unrelated information
B we are not concerned about the ease of climbing into the raft from water .It may true but we are just interested in whether the raft can hold 1500 lbs in relatively calm water.
D so we are gain not concerned about how the weight is distributed on the raft .
E Out of scope

The official answer is C but still i am unable to relate C with the argument
Hi mikemcgarry
Please explain the logic behind the choice .