GMAT Problem Solving Discussions

MBA
2317
roli64 Says
The answer will be 'c' as the negative values will be canceled, and since a+b

I would say just pick some negative values and try option c.
a=-3, b=-2, c=-1....these values satisfy aa+b=-5, b+c=-3 and (a+b)/(b+c) = -5/-3 = 5/3 = 1.66
Does this make sense?
2318
I would say just pick some negative values and try option c.
a=-3, b=-2, c=-1....these values satisfy aa+b=-5, b+c=-3 and (a+b)/(b+c) = -5/-3 = 5/3 = 1.66
Does this make sense?

I forgot the basic concept here... Thanks... 😃
2319
dreamscometrue Says
According to me the answer to this one should be E, anyone has any other answer. Please let me know. The correct answer according to most people is A, can anyone please explain how ?

8x(y^3) + 8 (x^3)y = /

What is xy?
(1) y>x
(2) x

lets solve the expression here and it will reduce to-
xy(x-y)^2=0
=>xy=0 or x=y

from statement one , we can conclude xy=0
from statment 2 nothing can be concluded.
So answer is A
2320
For aa) greater than 1
b) less than 1
c) greater than 0 but less than 1
d) greater than a/c
e) greater than -1

My take is a).


lets take a,b,c as -3,-2,-1

a+b=-5 and b+c=-3
so ratio=5/3
So answer is A.
2321

In a certain bathtub, both the cold-water and hot-water fixtures leak. The cold water leak alone would fill an empty bucket in c hours, and the hot-water leak alone would fill the same bucket in h hours, where cII. c III. c/2

  1. I only
  2. II only
  3. III only
  4. I and II
  5. I and III

The correct answer is I and III, but i am not able to understand why II is wrong and III is correct. Can anyone please guide?

2322
In a certain bathtub, both the cold-water and hot-water fixtures leak. The cold water leak alone would fill an empty bucket in c hours, and the hot-water leak alone would fill the same bucket in h hours, where cII. c III. c/2

  1. I only
  2. II only
  3. III only
  4. I and II
  5. I and III

The correct answer is I and III, but i am not able to understand why II is wrong and III is correct. Can anyone please guide?


here u can take value of c=1 & h= so value of t=.67

so from value of c,h & t u will tell option 1 & 3 satisfy....



Another method:-

c
2323

Aaahh..!! It got it now... 😃 Thanks for your reply...

2324

t=ch/(c+h); so t

2325
I got the answer wrong in the first attempt.. but then I could not even understand how they reached their answer (in the notes) which was different from my answer.. so just wanted to check on what answer do my fellow puys get.. ;)


There are two lines of defence against an attacking aircraft, the first is a missile and the second an anti-aircraft gun. The respective probabilities that the aircraft being hit by the missile and the gun are 2/9 and 1/8, respectively. What is the probability of hitting the aircraft?

Two girls have their birthdays in the same week. It is known that one of the girls was born on a Saturday, write down the sample space and hence determine the probability that both were born a Saturday.
2326
I got the answer wrong in the first attempt.. but then I could not even understand how they reached their answer (in the notes) which was different from my answer.. so just wanted to check on what answer do my fellow puys get.. ;)
There are two lines of defence against an attacking aircraft, the first is a missile and the second an anti-aircraft gun. The respective probabilities that the aircraft being hit by the missile and the gun are 2/9 and 1/8, respectively. What is the probability of hitting the aircraft?
Two girls have their birthdays in the same week. It is known that one of the girls was born on a Saturday, write down the sample space and hence determine the probability that both were born a Saturday.


1.hit by first line of defense+miss by first and hit by second line of defense
=2/9+7/9*1/8
=23/72

2.each girl is having 7 options to be born.out of these only one is favourable
=1/7*7
=1/49
2327
I got the answer wrong in the first attempt.. but then I could not even understand how they reached their answer (in the notes) which was different from my answer.. so just wanted to check on what answer do my fellow puys get.. ;)
1)There are two lines of defence against an attacking aircraft, the first is a missile and the second an anti-aircraft gun. The respective probabilities that the aircraft being hit by the missile and the gun are 2/9 and 1/8, respectively. What is the probability of hitting the aircraft?
2)Two girls have their birthdays in the same week. It is known that one of the girls was born on a Saturday, write down the sample space and hence determine the probability that both were born a Saturday.

Soln. question 1- P(E)=probability that aircraft being hit=1-P(E')=1-(7/9*7/8 )
P(E)=23/72

Soln question 2-P(e)=prob. to be born on Saturday=1/7*1/7=1/49
2328
I got the answer wrong in the first attempt.. but then I could not even understand how they reached their answer (in the notes) which was different from my answer.. so just wanted to check on what answer do my fellow puys get.. ;)
There are two lines of defence against an attacking aircraft, the first is a missile and the second an anti-aircraft gun. The respective probabilities that the aircraft being hit by the missile and the gun are 2/9 and 1/8, respectively. What is the probability of hitting the aircraft?
Two girls have their birthdays in the same week. It is known that one of the girls was born on a Saturday, write down the sample space and hence determine the probability that both were born a Saturday.


1. P(hitting aircraft) = exactly 1 hits the aircraft (i am assuming both, missile and gun wont hit aircraft simultaneously, even if one hits, job is done !!)

= missile hits and gun misses OR missile misses and gun hits
= 2/9*7/8 + 7/9*1/8
= 21/72 = 7/24

I dont think, 1 - both should be applicable here ..

2 ..We already know one of the girls is born on saturday, which one does not matter, so just 1 possibilty for one of the girls and 7 possibilities for the other one .

hence probability of overlap is 1/7..
2329

A cube of dimensions 3*3*3 is made from 27 cubes of 1*1*1.how many sets of 3 cubes can be obtained from this large cube with a straight line passing through their centers.

2330
1. P(hitting aircraft) = exactly 1 hits the aircraft (i am assuming both, missile and gun wont hit aircraft simultaneously, even if one hits, job is done !!)

= missile hits and gun misses OR missile misses and gun hits
= 2/9*7/8 + 7/9*1/8
= 21/72 = 7/24

I dont think, 1 - both should be applicable here ..

2 ..We already know one of the girls is born on saturday, which one does not matter, so just 1 possibilty for one of the girls and 7 possibilities for the other one .

hence probability of overlap is 1/7..


If you agree that if one of the machines hit then other is not required then y you have taken gun misses in the first part?will it make sense?

second part -ummmm I reckon u
2331
If you agree that if one of the machines hit then other is not required then y you have taken gun misses in the first part?will it make sense?

second part -ummmm I reckon u


Yes it does make sense ...

There are 2 ways to look at ths sum

1st : Exactly one hits the aircraft
2nd ; 1 - possibility both miss the target

Now, if we evaluate possibilty 2, it includes the possibilty that arcraft has been ht by both ...which i feel is incorrect ....

Now coming back to approach 1
exactly one method hts aircraft ,it implies one hits and other misses ...
Hence we do need to nclude gun misses when missile hits ....
2332
Yes it does make sense ...

There are 2 ways to look at ths sum

1st : Exactly one hits the aircraft
2nd ; 1 - possibility both miss the target

Now, if we evaluate possibilty 2, it includes the possibilty that arcraft has been ht by both ...which i feel is incorrect ....

Now coming back to approach 1
exactly one method hts aircraft ,it implies one hits and other misses ...
Hence we do need to nclude gun misses when missile hits ....


You will be right if we assume that anyone of the guns can fire first, but I think though its mathematicaaly correct but illogical.So cant say for certain
2333
rohitmodimodi Says
A cube of dimensions 3*3*3 is made from 27 cubes of 1*1*1.how many sets of 3 cubes can be obtained from this large cube with a straight line passing through their centers.

What is meant by passing through centre?
2334

What is the sum of all the internal angles of a 5 vertex star?
(Please check the attachment for a visual)

a. 45
b. 90
c. 180
d. 270
e. 360

2335
What is the sum of all the internal angles of a 5 vertex star?
(Please check the attachment for a visual)

a. 45
b. 90
c. 180
d. 270
e. 360


Hey ...i guess this is a poblem form OG ...Ans is C...180 degrees...

As per figure a,b,c,d,e are outer angles of star
Let v,w,x,y,z be the inner angles of star forming a pentagon.

Now, 1 inner angle and 2 outer angles make up a total of 5 triangles ..
these are:
a+c+v =180 ...
b+e+w=180
a+d+x=180
c+e+y=180
b+d+z=180

Hence, 2(a+b+c+d+e)+(v+w+x+y+z) = 900
now,(v+w+x+y+z) = 540 (pentagon)

Hence (a+b+c+d+e) = 180 ..
2336
What is the sum of all the internal angles of a 5 vertex star?
(Please check the attachment for a visual)

a. 45
b. 90
c. 180
d. 270
e. 360


See the attached figure for refrence-
In triangle BEF, angle F=180-B-E
and in triangle DGF, F=B+E
similiarly from triangle ACG,and triangle DGF, angle G=A+C
Sum of all triangles =180, so G+F+D=A+C+B+E+D=180