Ask me Anything about GMAT Quant and Math in General Hello and welcome to my PS Forum Expert Topic . Let me know if you have any Problem Solving questions I can help with - strategy, specific ones, etc. You may know me from forum discussion - I am one of the resident Veritas Prep Experts on GMAT Club. I have over 8,000 posts and 22,000 Kudos. I hope you find my replies and explanations helpful. My most helpful reply to this OG Question received over 100 Kudos. If you have any specific questions about PS or Math in general such as strategy, approach, etc, please feel free to post them here and I will be happy to address them. I intend to have this thread be as a "Everything You Need to Know about PS" type of thread and will include some FAQ's over time. Thank you all - good luck on the GMAT and look forward to seeing you in the PS forum! Karishma.

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

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indu1954

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01 Mar 2019, 08:58

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Hi Karishma,
Of 10 balls, 5 are red balls, 3 are blue balls, and 2 are yellow balls in a jar. If 2 balls are selected at random from the jar, what is the probability that one ball selected is red and the other ball is blue?
A. 1/5 B. 1/4 C. 1/3 D. 1/2 E. 2/3

bilaltariqakthar

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03 Mar 2019, 09:28

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Hi Karishma,

I have been facing difficulty in doing quant questions using the logical approach. I usually get the answers correct but I often use long and time consuming algebraic methods. Is there any material I should go through to get better at applying a logical approach to solve quant questions?

Thanks.

KarishmaB

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03 Mar 2019, 21:28

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indu1954

Probability of picking a red ball first = 5/10
Probability of picking a blue ball next = 3/9
Probability of picking a red and then a blue ball = (5/10)*(3/9) = 1/6

Probability of picking a blue ball first = 3/10
Probability of picking a red ball next = 5/9
Probability of picking a blue and then a red ball = (3/10)*(5/9) = 1/6

Probability of picking a red and a blue ball = (1/6) + (1/6) = 1/3

Answer (C)

KarishmaB

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Updated on: 19 Sep 2023, 04:37

Originally posted by KarishmaB on 03 Mar 2019, 21:34.
Last edited by KarishmaB on 19 Sep 2023, 04:37, edited 1 time in total.

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bilaltariqakthar

Hey bilaltariqakthar,

You should check out our blog here: https://anaprep.com/blogs/
and our videos here: https://www.youtube.com/channel/UCVxczp ... EUyt72G2Eg

We discuss lots of strategies for solving questions holistically.

bilaltariqakthar

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05 Mar 2019, 02:20

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Thank you Karishma for your response. I have started going through the blog. It's really helpful.

I have a quick question:

For how many values of x, is |x – 3| + 3|x + 1| + |x| = 4?

In your blog, you have said that the answer is 0. Could you please explain why?

KarishmaB

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05 Mar 2019, 02:42

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bilaltariqakthar

If you have understood the method explained in the blog, then consider this:

x is a point such that the sum of "distance of x from 3", "3 times the distance of x from -1" and "distance of x from 0" will be 4.
We know that distance of x from 3 to -1 is already 4 so when you add in the distance from 0, it will increase. There is no way the sum can be 4. It must be more than 4 in every case. Hence, the equation has no solutions.

rawat2583

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05 Mar 2019, 13:22

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Thanks Karishma ,
I need to ask one more question

1)Of 45 persons, 28 subscribed to the newspaper A, 17 did to the newspaper B, and 12 did to the newspaper C. 7 persons subscribed to both the newspaper A and the newspaper B, 8 did to both the newspaper B and the newspaper C, and 9 did to both the newspaper C and the newspaper A. If 6 persons did not subscribe all of the 3 newspapers, what is the number of the persons who subscribed only one newspaper?

A. 18 B. 21 C. 24 D. 27 E. 30

KarishmaB

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06 Mar 2019, 02:44

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rawat2583

First check this post on overlapping sets: https://www.gmatclub.com/forum/veritas-prep-resource-links-no-longer-available-399979.html#/2015/1 ... ping-sets/

Total = n(A) + n(B) + n(C) – n(A and B) – n(B and C) – n(C and A) + n(A and B and C) + n(No Set)

45 = 28 + 17 + 12 - 7 - 8 - 9 + n(A and B and C) + 6

n(A and B and C) = 6

n(Exactly one set) = n(A) + n(B) + n(C) – 2*n(A and B) – 2*n(B and C) – 2*n(C and A) + 3*n(A and B and C)
n(Exactly one set) = 28 + 17 + 12 - 2*7 - 2*8 - 2*9 + 3*6 = 27

P.S. - Please always send me the original question and the source too. Thanks!

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10 Mar 2019, 10:07

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VeritasKarishma

indu1954

Thanks Karishma

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13 Mar 2019, 20:12

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Hy Karishma,
I red your some post, which very helpful
I have been preparing since half year, i have given one attempt but score 440, i need just 600 score and have more one month.My split was Q40 and V15 which soo wiered please help me in boosting verbal to V30
I am lacking most at CR and SC which are crucial
I have one month plzzz help me out in this regard
How i can contact you on personal E-mail.

Posted from my mobile device

KarishmaB

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13 Mar 2019, 21:33

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SNHRY

Hey SNHRY,

Feel free to PM me by clicking on the "Send PM" link on the left hand side.

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Sorry karishma i m not finding Send PM link on the left side of this post
Please clear it how i can contact you.

ohhh sorry sorry iwas not getting in mobile now got it when login through laptop.
i have sent you PM please reply there
thank u

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19 Mar 2019, 10:25

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Hi karishma,
I need help in this question
1/ (statistics) 21 students took an exam. What is the number of students whose scores are at least the average (arithmetic mean) score of them?
1) The average (arithmetic mean) score of them is 78

2) The median score of them is 78

KarishmaB

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19 Mar 2019, 20:04

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Sandeepanisha

Hey Sandeepanisha,

We have 21 total students. We need those who scored >= Average

1) The average (arithmetic mean) score of them is 78
Not sufficient. We don't know how many scored at or above average and how many scored below average. There are many cases possible.
E.g. All 21 students scored exactly 78.
or 1 student scored 77, 19 students scored 78 and 1 student scored 79
and so on...
Number of students who scored >= average will be different in each case.

2) The median score of them is 78
Median score is the 11th score (middle) when all are arranged in increasing order. Again, multiple cases are possible.
E.g. All 21 students scored exactly 78. (so 11th score is also 78)
or 1 student scored 77, 19 students scored 78 and 1 student scored 79 etc (so 11th score is also 78)
and so on...
Number of students who scored >= average will be different in each case.

Using both statements, even if we know that the average is 78 and median is 78 too, still multiple cases are possible. Both examples discussed above hold and number of students who scored atleast average is different in both examples.

Answer (E)

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20 Mar 2019, 07:27

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Thanks karishma ,really appreciated your Help.
I need to ask one more Question

In the xy-plane, a circle with the center of the origin has the x- intercepts of P(50,0) and R(-50,0). If Q is a point on the circle, what is the length of PQ?

1) The x-coordinate of Q is -40

2) The y-coordinate of Q is -30

KarishmaB

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22 Mar 2019, 05:19

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Sandeepanisha

Since the circle has the centre at origin, the distance between the two x intercepts will give the diameter. So the diameter is 100. This means the radius of the circle is 50.

Attachment:

Screenshot 2019-03-22 at 16.34.18.png [ 19.27 KiB | Viewed 1777 times ]

For the length of PQ, we need the coordinates of P and Q. We already know that P(50, 0). Now we just need the coordinates of Q.

1) The x-coordinate of Q is -40

Note in the diagram above that there will be 2 points (Q' and Q'') on the circle which will have x coordinate of -40. But distance of each from P will be the same since Q' and Q'' are a reflection of each other across the x axis. So in both cases, PQ will be defined and will take the same value.
Hence this statement is sufficient alone.

2) The y-coordinate of Q is -30

Again, there will be 2 points (Q'' and Q''') where y coordinate will be -30.
Q'' will be much farther from P than Q''' so depending on the x co-ordinate of Q, the length of PQ will vary. Hence this statement is not sufficient alone.

Answer (A)

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23 Mar 2019, 19:01

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Thanks Karishma,
I have a quick question:

The 3 ships will transport goods. Of all of the goods, 1/3 is transported by the first ship. And, of the remained goods, 1/3 is transported by the second ship and also, of the remained goods after 2 times transports, 1/3 is transported by the third ship. If the remained goods are 40 tons finally, what is the total weight of the goods before transports, in tons, originally?

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23 Mar 2019, 19:03

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Hi Karishma,
In a certain flower bed, the flower X species with only green color and yellow color accounts for 3/8 of all flowers. If the flowers with green color account for 3/4 of the flower X species, what fraction of all flowers in the flower bed are yellow colors?

A. 1/32 B. 1/16 C. 3/32 D. 1/8 E. 5/32

KarishmaB

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24 Mar 2019, 21:22

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Sandeepanisha

Hey Sandeepanisha,

What is the source of this question? I don't know where the problem lies - Either the language of the original question is very unclear or you need to put down the question verbatim.

First ship => 1/3 goods
Remaining => 2/3 goods

Second ship => (1/3) of Remaining = (1/3)*(2/3) = 2/9
Remaining now => 2/3 - 2/9 = 4/9

Third ship => (1/3) of (4/9) = 4/27
Remaining now => 4/9 - 4/27 = 8/27

This Remaining now (8/27 of total originally) is given to be 40 tonnes
Total originally = 40*(27/8) = 135 tonnes

KarishmaB

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24 Mar 2019, 21:28

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Sandeepanisha

Same comment for this question too.

Say there are total 32 flowers.

Flower X = (3/8)*32 = 12

Green colour accounts for (3/4)th of 12 so yellow account for (1/4)*12 = 3 flowers.

Fraction of yellow flowers = 3/32