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

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,

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.

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.

Hello from the GMAT Club BumpBot!

Thanks to another GMAT Club member, I have just discovered this valuable topic, yet it had no discussion for over a year. I am now bumping it up - doing my job. I think you may find it valuable (esp those replies with Kudos).

Want to see all other topics I dig out? Follow me (click follow button on profile). You will receive a summary of all topics I bump in your profile area as well as via email.