Andy owned farmland adjoining a 19-foot-high bank of a lake.

Question

Andy owned farmland adjoining a 19-foot-high bank of a lake. He considered two pumps for installation—Pump A and Pump B. Pump A had to be continuously immersed in the water source—at least 13 feet above the bottom of the source. The lower-cost pump, Pump B, had to be placed outside the water source—at a height not exceeding 18 feet above the source. For reliable functioning, both pumps needed to be full of water to exclude trapped air. Given that the outputs, durability, and the costs of purchase, maintenance, and operation of both pumps differ insignificantly, which pump should Andy have chosen?

(1) The lake has water at least 18 feet deep throughout the year.
(2) The lake sometimes floods Andy's end of the bank during a certain time of the year.

GMATslaughter100 · Answer

KarishmaB   RonPurewal   MartyMurray   GMATNinja   WhitEngagePrep 
Hi experts, this one is interesting, would you help shed some light on it?

My thought process is that, (1) only tells us Pump A is feasible, but does not tell us Andy has to choose Pump A, since we don't know what he cares the most. (2) goes with the same reason. So I think even those 2 conditions combined cannot lead to sufficiency. We should choose E.

But I am also confused with A, since if Pump B cannot be hang on somewhere above the water surface but below the top the bank, let's say Pump B can only be put on the farmland, then Pump B can never meet its requirement. That makes only (1) is sufficient. We should choose A.

How should we interpret this kind of GMAT question? Thanks in advance!

yashsharma1 · Answer

Could not understand the answer

1. Pump A will always be able to pump water but for pump B, as the height of water is at least 18 feet throughout the year, if it is 18, then pump B is preferable but if it is more than 18 feet, pump B cannot be used.

2. When sometimes the lake floods, pump B will not be usable. Hence for year round operation, only pump A is feasible.

Can someone help answer

svsivakrishna · Answer

I guess for statement 2:

sometimes when the lake floods, pump B cannot be used. 
Also, since this is a data sufficiency question, we need to arrive at a solution which clearly states, either pump A or pump B can be used. However, from statement 2, it can be interpreted that, if the lake does not flood and has minimum of 13 feet water at a particular period of the year, then pump A can be used, and in other case where the lake has a level of less than 13 feet , we can use pump B. so , here we are arriving at two options, ie., both pumps A and B at different times of the year,
hence this statement is insufficient.

Experts can correct me if my approach is wrong.

RonPurewal · Answer

This problem is a mess😒

• The given information is so poorly written that it's difficult to comprehend in general. 
Some of it, I genuinely have no clue how to interpret. The meaning of "both pumps need to be full of water to exclude trapped air", for instance, is a complete mystery to me; I'm not immediately able to understand that statement in any way that doesn't seem to contradict the fact that "Pump B ... has to be placed outside the water source". So I just ignored that part... la la la ̄\_(ツ)_/ ̄

• To take things from bad to worse, the wording isn't even consistent from one sentence to another—e.g., "at least 13 feet  above the bottom of the source " and "at least 18 feet  above the source " are meant to be two instances of the same kind of measurement (...or at least I  think  they are... hahah), a realization it's hard to make with confidence given the differing phrasings.

• To take the next step from worse to downright infuriating, the given information explicitly contradicts itself! We're told that Pump B is "the lower-cost pump", even though "the costs ... do not significantly differ" between the two pumps. Huh? ( •᷄‎ࡇ•᷅ )

.

With so many problems baked into the problem statement itself, you'd do well to just skip this one entirely. Buuuuutttt... here's my best attempt to read the problem in a way that actually makes enough sense to be solvable, and then to solve it.

Here's how I decided to interpret the givens. (These interpretations are NOT authoritative! If you read the given statements quite differently, there's a very good chance that your interpretation is justified too.)

Pump A had to be continuously immersed in the water source—at least 13 feet above the bottom of the source. 
—> I took this to mean that Pump A has to be anchored to the bottom of the lake, and that its total height has to be less than the depth of the lake at all times (so that the entire apparatus is completely underwater at all times). Under that interpretation, it follows that  we can only use Pump A if the depth of the lake NEVER goes below 13 feet  at any time ever.

Pump B, had to be placed outside the water source— 
—> Yeaaaahhhh... okay.
First of all, it's not clear whether this means "above the surface of the lake (but installed into the lake bottom)" or "actually OUTSIDE the lake" (the latter of which seems pretty weird to my intuition, but statement 2—which talks about the lake overflowing its banks—encourages that line of thought). I also can't say with any certainty how either of these possibilities would interact with the requirement that the pump be "full of water" in perpetuity (a statement I frankly had no idea how to use).

at a height not exceeding 18 feet above the source. 
—> I'll assume that this is a height above the BOTTOM of the source, like the 13 feet above.
Unfortunately, this condition COULD be consistent with either of the two interpretations above. (We can clearly read it together with the idea that Pump B is installed into the bottom of the lake but sits above the surface. It may seem at first glance to contradict the "outside the lake itself" interpretation—since the banks of the lake are 19 feet above the bottom—but we don't know whether the land slopes back downward on Andy's side after cresting the 19-foot bank. If it does so, then the sometimes-flooded land described in statement 2 COULD lie at an elevation that's less than 18 feet above that of the lake bottom.)
Buuuutttt... the second interpretation can't be used in any way that's definite (since we know nothing about the topography of Andy's land near the lakefront). So,  I guess I'll go with the first interpretation—which means that, if the lake is 18 FEET DEEP OR DEEPER, then we CAN'T use pump B  as it would then be submerged.

.

Mmmmmkay. With  that  set of interpretations (which, once again, is far from the only way you could've read the given information....):

—> If the givens mean what I wrote above, then this statement tells us both that we can ALWAYS use Pump A, AND that we can NEVER use Pump B. This is nice, since it's "sufficient" regardless of whether the question is asking which pump we COULD use or which pump we MUST use (another ambiguity!). Yay! Whoo hoo! Sufficient.

—> So we know that the lake is 19 feet deep at certain times of year. "Sometimes", however, is not good enough to determine sufficiency, since literally anything could happen during the rest of the year (the lake might even dry up completely in the summer, for all we know). And, on top of that, we still don't know anything about the topography of the flooded land—although the specs of the flooded land are only relevant if my SECOND interpretation of the rules for Pump B (the one I didn't use here... lol) is actually what was meant here.
No matter what, though, we're not getting sufficiency out of this one.

.

So, overall, A... if you make all 99,999 of the assumptions I did in interpreting the paragraph. >____<

GMATslaughter100 · Answer

Wow, I really appreciate your answer and discussion. This certainly inspires us.

Andy owned farmland adjoining a 19-foot-high bank of a lake.

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Andy owned farmland adjoining a 19-foot-high bank of a lake.

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