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

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!

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

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

A car travels from town A to town B at constant speed. If it increases speed by 20%, it will arrive 1 hour ahead of schedule.If it increased by 25% after travelling the first 120 km at usual speed,it will arrive 36 minutes ahead.Find the distance from A to B.

a.205
b.210
c.230
d.220
e.250

Posted from my mobile device

Given:
1. A car travels from town A to town B at constant speed.
2. If it increases speed by 20%, it will arrive 1 hour ahead of schedule.
2. If it increased by 25% after travelling the first 120 km at usual speed,it will arrive 36 minutes ahead.

Asked: Find the distance from A to B.

Let the distance from A to B be x km and normal speed of the car be v kmh

x/1.2v = x/v - 1 (1)
x/v = 6 => 1/v = x/6
x = 6v (1a)
\(\frac{x-120}{1.25v} = \frac{x-120}{v} - \frac{36}{60}\) (2)
(x-120)/v = 36*5/60 = 3
x -120 = 3v = x/2
x = 240

Distance from A to B = 240 km

None of the choices match the correct answer.

Thank You very much. I really appreciate

When distance travelled is the same, ratio of speeds is inverse of ratio of time taken.

Case 1: When car increases its speed by 20% over the entire distance.
Ratio of speeds = 5:6 (20% increase in speed), ratio of time taken = 6:5
The actual difference in time taken is 1 hr so in usual case, the car takes 6 hrs but with increased speed, it will take 5 hrs.

Case 2: When car increases its speed by 25% over second part of the distance (ignore the first 120 kms for the time being)
Over the distance that the car increases its speed by 25%, ratio of speeds = 4:5 (increase of 25%)
Then ratio of time taken = 5:4 (a difference of 1 on ratio scale)
The actual difference in time taken is 36 mins = 36/60 hrs = 3/5 hrs. So normally, the car takes 5*(3/5) hrs = 3 hrs over this distance.

Now note that for the entire distance, the car usually takes 6 hrs. For the second part distance, the car usually takes 3 hrs. So this second part distance must be exactly 1/2 of total distance.
Hence total distance must be 2*120 km = 240 km