Problem Solving

There are 28 students in a class. The first student draws a line of length 'a' units on the black board of the class. The second student draws a line of length 'b' units (a is not equal to b) on the black board of the class. The third student draws a line whose length is the average of the lengths of the two lines that are drawn by the first and second student on the black board. The fourth student draws a line whose length is the average of the lengths of the lines that are drawn by the first, second and third student. This process of drawing lines on the black board continues till the twenty-eighth student of the class. How many students drew the line having the same length?

A) 5/12(a + b)
B) 28(a + b)
C) 26
D) 14
E) None of these
CA ans would be posted after some discussion

Reading the question first time, I thought of replying "man....hang on, let me finish my Tea, to prepare my mind..."

but then thought, lets try it....seems turned out very simple

Answer = C

let me give explanation after finishing Tea....i deserve it now

explanation:

first 3 students == a, b, (a+b)/2

4th student == 1/3 [ a+b+ (a+b)/2] = (a+b)/2

a, b, (a+b)/2, (a+b)/2

5th student == 1/4 [ a+b+ (a+b)/2 + (a+b)/2] = (a+b)/2

it goes on... from 3rd student onwards, everyone draws (a+b)/2

are you going to give me "Thanks" or finding some serious flaw in my answer if not, then press "Thanks" button, buddy

Shashank, can you provide OA at least?? if not thanks

See this question was very simple gmat700. you just have to see what is the trick behind it..as I already pput in header the question is tricky...you could have taken courage to read it....
I think 30 sec for reading and 20 sec for solving it...don't u think so...
well ur answer is correct after 2 students all 26 students went on drawing same length...Sometimes GMAT also test reading skill..and whenever u find a question witha a lot of words..it is sure to take less time than any other smaller question..as I have observed...so don't go for a tea break.rather break the question in smal pieces and u wiil have ans without pena and paper..
So Ans is C

Hmmmm... I agree and thats why I had put earlier that it turned out to be very simple question....

but let me ask you one thing - what for you post question, if you find it simple and know the solution and approach everything??

....I observed this in most of your today's questions that you posted..

As I understand, this forum is for sharing questions where you had difficulty answering or finding proper explanation... to get help from others..


Trust me, I am not writing this because you did not give thanks to me ...

think over it and then act in the true spirit of this forum....there are so many people who want to beat the GMAT and have genuine problem and difficulty understanding certain concepts, questions...BUT attention (by others) to those
genuinely-requested-HELP gets diluted or even missed in the flood of such "for the sake of playing and challenging others"-kindda questions... I am not saying you MUST NOT post such question (where you are not truly looking for help) but try cut down situation where in a day you post many such, as I observed today....

again, dont take me wrong buddy....I genuinely felt that its impacting those who are in REAL NEED to get some help...

I am not sure how others see this kind of posting....will wait for others view as well...especially, would be interested to see view from moderator...

I found out this problem very interesting when I tried to solve it ..I was initially tensed to see such a big problem..
but when I solved it within 2 minutes I was very happy ..so I though I should share it to others..so that other can get a good point out of it...
Also for other problems..I have tried to solve problems posted by others..who are in need...so all people who come here gets their solution MP..

@Shashank,

We may not hold on to forum for years....but the discipline u get here will go far way!!

Treat this as a learning experience & post questions which u feel resembles GMAT Prep/Real GMAT test /OG patterns.

I am no one to suggest you. But at times i did heard wrath of other users yelling abt your post.

I know couple of users who queries were never answered because people over here boycotted him.

U r posts are good. I wish u make them superb.

I suppose even @Ajith gave red herring to u sometime.Ajith is a strong veteran for this forum and a IIM guy too. SO Plz do understand the level of difficuty u have caused to people with our ur knowledge.

Just this is a small tip which may be helpful for u when u get in to your MBA school also where u need to "Listen " a lot to speak a lot!!

Thanks Gmatmochan I liked ur idea, and i will try to be superb here.......yeah but ajith supported me a lot many time.
.So Ajith is studying at some IIM ...thats cool....so why is he preparing for GMAT then...he is already at a primere place..I suppose..