Some technical and brainteaser questions I need help on

Not sure you worded the 1st question right, but if you have a 10x10x10 cube, and you remove the outermost layer, you end up removing 2 rows, 2 columns, and 2 ... whatever the other dimension is. Think of a 3x3x3 cube, there is only a 1x1x1 cube in the middle.

For the 2nd question, you've gone 60 miles in 2 hours. You now want to go 60 miles more, for a total of 120 miles. In order to go 120 miles at an average of 60mph, you need to do the trip in 2 hours (120mph/2hrs = 60mph). However, 2 hours have already elapsed. What this means is you need to drive the remaining 60 miles "instantaneously," which clearly isn't possible.

~~~~~~~~~~~
CompBanker

2. Think about it. In order for the car to average 60mph, he would have to travel 2 hours in total (roundtrip). Since he already took 2 hours to go one way, it's impossible to average 60mph.

And I believe you misunderstood question #1. I think the problem asks if you paint ALL sides of the cube.

http://www.ibankingfaq.com/category/interviewing-brainteasers/

You’ve got a 10 x 10 x 10 cube made up of 1 x 1 x 1 smaller cubes. The outside of the larger cube is completely painted red. On how many of the smaller cubes is there any red paint?

First, note that the larger cube is made up of 1000 smaller cubes. The easiest way to think about this is how many cubes are NOT painted? 8 x 8 x 8 inner cubes are not painted which equals 512 cubes. Therefore, 1000 - 512 = 488 cubes that have some paint. Alternatively, we can calculate this by saying that two 10 x 10 sides are painted (200) plus two 10 x 8 sides (160) plus two 8 x 8 sides (128). 200 + 160 + 128 = 488.

And:

A car travels a distance of 60 miles at an average speed of 30 mph. How fast would the car have to travel the same 60 mile distance home to average 60 mph over the entire trip?

Most people say 90 mph but this is actually a trick question! The first leg of the trip covers 60 miles at an average speed of 30 mph. So, this means the car traveled for 2 hours (60/30). In order for the car to average 60 mph over 120 miles, it would have to travel for exactly 2 hours (120/60). Since the car has already traveled for 2 hours, it is impossible for it to average 60 mph over the entire trip.

If you're having trouble understanding the first one, think of a smaller cube to start. If you're having trouble with the second one, think of how the average mph changes. Oh, and the 60 miles is distance in the first one, not "60 miles per hour". Hope that helps.

wait... you couldn't answer these questions...? and you got interviews...? w-t-f??

LOL I was thinking the same thing... no justice

I can't wait for the day that b2 can't answer a brainteaser in an interview. I always thought brainteasers were the silliest questions, and way less useful than technical or fit questions.

I've had probably around 20-25 interviews for investment banking, and in all those interviews I've gotten 1 brainteaser.

I see the point of not being able to have an average speed of 60mph because two hours have already passed. However, that is an average based on time. For an average speed based on distance you could travel at 90. Point this distinction out to the interviewer and you'll likely get extra points.

This question is easy as shit. If you've studied for the GMAT before, questions like these wouldn't trick you at all.