GMAT Problem Solving Discussions

MBA
3741
Hi,
Can you help me with this? Please explain the method to reach the answers.

Q . A student is allowed to select at the most X books from a collection of (2X+1) books. If the total number of ways in which he can select book is 63,find the value of X.

Thanks
pj02


First let us assume a value for X.
x = 3.So ,2x+1 = 7.Atmost the student can select 3 books from 7 books.
There are 3 cases

1 book selected = no.of ways = 7c1 = 7
2 books selected = no.of ways = 7c2 = 21
3 books selected = no.of ways = 7c3 = 35

total no.of ways = 63.So the value of x = 3.
3742
First let us assume a value for X.
x = 3.So ,2x+1 = 7.Atmost the student can select 3 books from 7 books.
There are 3 cases

1 book selected = no.of ways = 7c1 = 7
2 books selected = no.of ways = 7c2 = 21
3 books selected = no.of ways = 7c3 = 35

total no.of ways = 63.So the value of x = 3.


What makes you assume the value of x=3 ?
3743
pj02 Says
What makes you assume the value of x=3 ?


Its a professional guess where you start with certain values.In this case,I tried for the atmost case with x=3 and x=4.

7C3 = 35 9c4 = 126 > 63

-Deepak.
3744
There are 27 different three-digit integers that can be formed using only the digits 1, 2 and 3. If all 27 of the integers were listed, what would their sum be?

a) 2,704

b) 2,990

c) 5,404

d) 5,444

e) 5,994


Can you please post the OA for the above q?
3745
deepakraam Says
Can you please post the OA for the above q?


be confident man, u were right...how could u be possibly wrong... OA is E.5994.
3746
First let us assume a value for X.
x = 3.So ,2x+1 = 7.Atmost the student can select 3 books from 7 books.
There are 3 cases

1 book selected = no.of ways = 7c1 = 7
2 books selected = no.of ways = 7c2 = 21
3 books selected = no.of ways = 7c3 = 35

total no.of ways = 63.So the value of x = 3.

Hey,

the student is allowed to select at the most 3 books. so dnt we have a case whr the student selects no book at all? (7c0)

thanks.
3747

A circle is inscribed in equilateral triangle ABC so that point D lies on the circle and on line segment AC and point E lies on the circle and line segment AB. If AB=6, what is the area of the figure created by line segments AD, AE and minor arc DE?

3748

if f(a+b) = f(a) +f(b), then which of the following could be f(x) for all distinct values of a and b?
1) x^2 + 1
2)2 sqrt(x)
3)x-4
4)5/x
5) -7x

3749
if f(a+b) = f(b) +f(b), then which of the following could be f(x) for all distinct values of a and b?
1) x^2 + 1
2)2 sqrt(x)
3)x-4
4)5/x
5) -7x


Firstly,check your question.It should most probably be f(a+b)=f(a)+f(b).Assuming that it is f(a)I think,it should be option 5).But i'm not sure.Just tried by hit n trial method by putting different values in the function.
3750
MissionPGPX Says
A circle is inscribed in equilateral triangle ABC so that point D lies on the circle and on line segment AC and point E lies on the circle and line segment AB. If AB=6, what is the area of the figure created by line segments AD, AE and minor arc DE?

3(SQRT(3) - pie/2)

What is the OA?
3751
3(SQRT(3) - pie/2)

What is the OA?


u made a mistake somewhere. OA is 3sqrt(3) - pie.
Area asked here is effectively = (area of triangle - area of circle) / 3

area of triangle = 9sqrt(3)
area of circle = 3pie
so area asked = 3sqrt(3) - pie.
3752

I am not sure I understand this correct.
What is the basis of (area of triangle -area of circle)/3

Effectively the solution should be:
Area of Equilateral Traingle(with side = 3) - ((Area of circle/3) - (area of traingle - 30-60-90 triangle))
= SQRT(3)/4*9 - (3pie - 3)

3753
I am not sure I understand this correct.
What is the basis of (area of triangle -area of circle)/3

Effectively the solution should be:
Area of Equilateral Traingle(with side = 3) - ((Area of circle/3) - (area of traingle - 30-60-90 triangle))
= SQRT(3)/4*9 - (3pie - 3)


i believe u r misreading the question. it asks you the area contained by line AD, AE and minor arc DE.... if u draw the figure u will have 3 empty corners created after shading the circle area, and we are asked area of such 1 space... hope its clear now...
3754

hi guys.. plz help me out wid these questions..

for a certain examination , a score of 58 was 2 standard deviations below the mean, and a score of 98 was 3 standard deviations above the mean. wat was the mean score for the examination? (explanation - a must)

a. 74
b. 76
c. 78
d. 80
e. 82

in addition, posting some basic fundas on standard deviations will be of immense help.

thanks in advance.

3755

is the ans a?

3756
hi guys.. plz help me out wid these questions..

for a certain examination , a score of 58 was 2 standard deviations below the mean, and a score of 98 was 3 standard deviations above the mean. wat was the mean score for the examination? (explanation - a must)

a. 74
b. 76
c. 78
d. 80
e. 82

in addition, posting some basic fundas on standard deviations will be of immense help.

thanks in advance.



Let M=mean
x=SD
Then M=58+2x or M=98-3x
So,
58+2x=98-3x
.
. . x=8

so M=74 or option a.
3757
Let M=mean
x=SD
Then M=58+2x or M=98-3x
So,
58+2x=98-3x
.
. . x=8

so M=74 or option a.


was it so simple????
3758

ya this was exactly how i solved it.....
i noticed one thing......not many books give much practice for stats ques....that is the rsn ppl feel unconfortale wit stats ques....otherwise ques asked on stats are quite simple

3759

Can somebody pls suggest a short method for solving this question:

Q - A crew can row a certain course upstream in 84 min; they can row the same course downstream in 9 minutes less than they can row it in still water. How long will they take to row down with the stream?

3760
Can somebody pls suggest a short method for solving this question:

Q - A crew can row a certain course upstream in 84 min; they can row the same course downstream in 9 minutes less than they can row it in still water. How long will they take to row down with the stream?


either some data is missing or i m solving it the wrong way..
can u post the options??