Submarine A and Submarine B are equipped with sonar devices that can

Question

Submarine A and Submarine B are equipped with sonar devices that can operate within a 3,000 yard range. Submarine A remains in place while Submarine B moves 2,400 yards south from Submarine A. Submarine B then changes course and moves due east, stopping at the maximum range of the sonar devices. In which of the following directions can Submarine B continue to move and still be within the sonar range of Submarine A?

I. North
II. South
III. West

A) I only
B) II only
C) I and II only
D) II and III only
E) I and III only

Kudos for a correct solution.

I. North
II. South
III. West

A) I only
B) II only
C) I and II only
D) II and III only
E) I and III only

Kudos for a correct  solution .

smit29may · Answer

Choice E. 
It's evident if we make a diagram for the Movement of B respect to A.

From its South position to the east position, it has covered the maximum radius for the south direction. Similarly, it's east movement further will also make it out of range.

Thus it can only move north or west or anything in that curve. 
Thus answer is E.

https://gmatclub.com/static/posted_from.png     Posted from    GMAT ToolKit

King407 · Answer

North and West.

Answer E

lipsi18 · Answer

Just draw a picture on paper it will be look like this: submarine A is the center of the circle & submarine B is on the circumference of the circle, after moving south and east from A. And currently on maximum distance to be in rage. So B can only move in this circular path, that is :
1. North
2. West

Hence option 1 and 3
Hence answer is E

Thanks,

Bunuel · Answer

The submarines have a 3,000 yard sonar range in all directions, which essentially makes a circle around the ship. Submarine B moves a certain number of yards south and then a certain number of yards east. The question then asks which direction the sub could move in without losing contact. This seems like a geometry question, and there are some numbers provided in this question. Let’s look through it quickly for the sake of completion, but you may have already noticed they won’t help in any meaningful way and are only there to bait you into tedious calculations. If submarine A has a circular range of 3,000 yards and submarine B moves south for 2,400 yards and then east, how far will it go east? The answer is actually a triangle inscribed within a circle, something like the figure below. Figure1.png Given that submarine B ends up at the edge of the 3,000 yard range, the hypotenuse of the triangle is 3,000 yards, and the y-axis is 2,400 yards. The x-axis displacement is easy to calculate if you recognize this pattern as a glorified 3-4-5 triangle. Multiply those values by 600 and you get an 1,800-2,400-3,000 right triangle. Thus the sub moved east by exactly 1,800 yards. However, this information won’t really be helpful in answering the question as we’re being asked for directions, not distances. The graph may help clarify the issue, but you can solve it without even using the graph either. Clearly the sub on the edge of the triangle can head back west and be within sonar range. Similarly, it can travel due north and stay within range as well. The only two directions that are not allowed are east and south. The answer must this be I and III together, which is answer choice E (also Kanye West’s daughter). While proficiency in mathematics is helpful on the GMAT (and in life in general), it is often not a necessary skill in solving “math” questions on the exam. Remember that the main goal is to test your reasoning skills and determine whether you can correctly solve problems. Being a business student isn’t about being an expert at math, but rather using the information provided to swiftly reach the correct conclusion. Oftentimes, the better you are at math, the less math you’ll actually end up using.

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Submarine A and Submarine B are equipped with sonar devices that can

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