Veritas Prep PS Forum Expert - Karishma - Ask Me Anything about Math

Need help to Solve the quant Question.

https://gmatclub.com/forum/geometry-297755.html

I don't understand this question. It seems to say that one person runs 10 rounds outside and another person runs 10 rounds inside. If the difference in the circumference is 15 feet, the one outside will run 10*15 feet extra. If the difference of 15 feet is between radii or diameter, it will be different. The question needs to clarify properly.

Hey ajaysharma121,

This link is broken. Can you please repost it?

Done.

Hi Karishma can you please help me with this?
https://gmatclub.com/forum/geometry-297753.html

Hey indu1954,

The requested post doesn't exist anymore. Could you please check!

Hi Karishma,

Weighted average is a gray area section for me, can you please help me in this problem.

https://gmatclub.com/forum/1-unit-of-x- ... 96986.html

Posted from my mobile device

Hey Shef08,

Done here: https://gmatclub.com/forum/1-unit-of-x- ... l#p2292835

If you struggle with weighted averages, check out this post: https://www.gmatclub.com/forum/veritas-prep-resource-links-no-longer-available-399979.html#/2011/0 ... -averages/

Hi VeritasKarishma, Can you please tell me most important quant topics I need to cover. I have a booked GMAT next week. I thought I was good at quant so I concentrated mostly on my verbal ability. Now my mock score is only 45. My target is 50/51. I am ready to put in 100 hours this week.Thanks!

Number Properties, Algebra and Geometry are the most important topics. Also, ensure that you understand the Data Sufficiency format really well. What is sufficiency, how to avoid common traps etc.

Hi VeritasKarishma

I had a doubt and its not clear to me yet.

If xyz ≠ 0, xy > 0, and x^2 + xy + xz < 0, then which of the following must be true?

I. x(y + z) < 0

II. x + y + z < 0

III. If x < 0, then z > 0.

A) I only
B) I and II only
C) I and III only
D) II and III only
E) I, II, and III

Can you please help me simplify why it cannot be E

xyz ≠ 0 implies none of x, y and z is 0.

xy > 0 implies both x and y have the same sign. Either both are positive or both negative.

x^2 + xy + xz < 0 implies xz is negative so x and z have opposite signs. x^2 is positive because squares cannot be negative. xy is positive we have already benn given so xz must be negative.

I. x(y + z) < 0

We know that the expression x^2 + xy + xz is negative
x^2 must be positive. So if we remove x^2 from above, the expression (xy + xz) will become even more negative.
Hence, this must be true.

II. x + y + z < 0
x^2 + xy + xz < 0
x(x + y + z) < 0
If x is positive, (x+y+z) < 0
If x is negative, (x + y + z) > 0 (Take x = -3, y = -1 and z = 100 for example)
So this is not necessarily true.

III. If x < 0, then z > 0.
Correct. x and z have opposite signs. So this must be true.

Answer (C)

hi VeritasKarishma

The product of 3 consecutive positive multiples of 4 must be divisible by each of the following EXCEPT:

A)16
B)36
C)48
D)128
E)192

The OA is B but i don't understand why exactly.
Arent all these numbers divisible by three consecutive multiples of 4

Say the 3 consecutive multiples are 4, 8 and 12. Their product = 4*8*12. This product is not divisible by 36.
36 = 4*9
The product does not have 9 in it (two 3s). It necessarily will have one 3 but it may or may not have two 3s. Hence it may not be divisible by 36.

Three consecutive multiples of 4 will have three 4s, another 2 and a 3 necessarily. So the product will be divisible by 2^7 * 3 and all its factors.

For more on this, check:
https://www.gmatclub.com/forum/veritas-prep-resource-links-no-longer-available-399979.html#/2011/0 ... c-or-math/
https://www.gmatclub.com/forum/veritas-prep-resource-links-no-longer-available-399979.html#/2011/0 ... h-part-ii/

Hiii VeritasKarishma


https://gmatclub.com/forum/if-6-4-x-5-w ... 99799.html

Referring to the question on this page

i am really confused when they say " |x|=-x " isn't the only possibility to this that x = 0???

because no number inside a mod sign can be negative as such

Hi Karishma.. I request reference to Question 1 in your post "A group of 8 friends sit together in a circle. If A refuses to sit beside B unless C sits on the other side of A as well, how many possible seating arrangements are possible?" Even though i understood your explanation, can u please tell me whats wrong in my approach?

My Approach: There are 2 scenarios possible, One where A sits next to both B & C and the other wherein A doesn't sit next to both B & C . In the former the no.of arrangements are: 1*2*1*5*4*3*2*1= 2*5!
In the latter the no. of arrangements are: 1*5*4*5*4*3*2*1= 20*5!
Thus total no. of arrangements are: 5!(20+2)= 22*5!
However your answer is 32*5!

Where am i missing??

Your assumption is that x is a positive number and hence, -x is a negative number. But can -x be a POSITIVE number? Think about it.

What about the case when x = -5? Then -x = - (-5) = 5

What about the case when x = -23? Then -x = - (-23) = 23

-x can be positive when x is negative. In these cases, -x = |x|

And hence, we define |x| as:

|x| = x when x >= 0
|x| = -x when x < 0