GMAT Question of the Day - Daily to your Mailbox; hard ones only

 It is currently 21 Oct 2019, 21:53 GMAT Club Daily Prep

Thank you for using the timer - this advanced tool can estimate your performance and suggest more practice questions. We have subscribed you to Daily Prep Questions via email.

Customized
for You

we will pick new questions that match your level based on your Timer History

Track

every week, we’ll send you an estimated GMAT score based on your performance

Practice
Pays

we will pick new questions that match your level based on your Timer History

Not interested in getting valuable practice questions and articles delivered to your email? No problem, unsubscribe here.  The Ultimate Q51 Guide [Expert Level]

 new topic post reply Question banks Downloads My Bookmarks Reviews Important topics
Author Message
Intern  Joined: 13 Jun 2017
Posts: 1
Re: The Ultimate Q51 Guide [Expert Level]  [#permalink]

Show Tags

Can someone please explain how the answer to the following DS question is A?

There are five homes. If the median price of a home is \$200,000, is the range of all prices greater than \$80,000?
1) The average price of the five homes is \$240,000.
2) Three of five homes have the same price.
Math Revolution GMAT Instructor V
Joined: 16 Aug 2015
Posts: 8025
GMAT 1: 760 Q51 V42 GPA: 3.82
Re: The Ultimate Q51 Guide [Expert Level]  [#permalink]

Show Tags

If x, y are integers, is x+y an odd number?

1) y=3x+5
2) y=2x-3

==> If you modify the original condition and the question, in order to get x+y=odd, you need to get (x,y)=(even,odd)or (odd,even). For con 1), you get (x,y)=(even,odd) or (odd, even), hence always yes and sufficient.

Therefore, the answer is A.
_________________
Math Revolution GMAT Instructor V
Joined: 16 Aug 2015
Posts: 8025
GMAT 1: 760 Q51 V42 GPA: 3.82
Re: The Ultimate Q51 Guide [Expert Level]  [#permalink]

Show Tags

What is the number of multiples of 6 from -35 to 69?

A. 14
B. 16
C. 17
D. 20
E. 21

==> 0 becomes the multiple of all integers. From 1~69, 11 of them are multiples of 6, from -1~-35, 5 of them are multiples of 6, hence you get 11+5+1=17.

The answer is C.
_________________
Math Revolution GMAT Instructor V
Joined: 16 Aug 2015
Posts: 8025
GMAT 1: 760 Q51 V42 GPA: 3.82
Re: The Ultimate Q51 Guide [Expert Level]  [#permalink]

Show Tags

√75+2√3=?

A. 3√3
B. 5√3
C. 7√3
D. 8√3
E. 9√3

==> You get √75+2√3=√(5^2)3+2√3=5√3+2√3=7√3.

The answer is C.
_________________
Math Revolution GMAT Instructor V
Joined: 16 Aug 2015
Posts: 8025
GMAT 1: 760 Q51 V42 GPA: 3.82
Re: The Ultimate Q51 Guide [Expert Level]  [#permalink]

Show Tags

Is ab+cd>0?

1) ac+bd＞0

==> In the original condition, there are 4 variables (a, b, c, d), and in order to match the number of variables to the number of equations, there must be 4 equations. Since there is 1 for con 1) and 1 for con 2), E is most likely to be the answer. By solving con 1) and con 2), you get a=2, b=3, c=-1, d=2: yes BUT a=5,b=-1,c=1,d=2:, hence it is not sufficient.

Therefore, the answer is E.
_________________
Math Revolution GMAT Instructor V
Joined: 16 Aug 2015
Posts: 8025
GMAT 1: 760 Q51 V42 GPA: 3.82
Re: The Ultimate Q51 Guide [Expert Level]  [#permalink]

Show Tags

If x/100+x/1,000+x/10,000+x/100,000=111, what is the approximation of x?

A. 11,100
B. 111,000
C. 1,111,000
D. 11,111,000
E. 111,111,000

==> Since it is approximation, you get _. Then, only x/100=111 is left, and thus you get x=11,100.

The answer is A.
_________________
Math Revolution GMAT Instructor V
Joined: 16 Aug 2015
Posts: 8025
GMAT 1: 760 Q51 V42 GPA: 3.82
Re: The Ultimate Q51 Guide [Expert Level]  [#permalink]

Show Tags

If average (arithmetic mean) score of 9 students is 90, what is the median score?

1) The 5 smallest scores are 84, 83, 82, 81, and 80
2) The 4 largest scores are 89, 88, 86, and 85

==> If you modify the original condition and the question, and list the 9 numbers in the ascending order, you get 5th=median. Thus, according to con 1), you get 5th=median=84.

Therefore, the answer is A.
_________________
Math Revolution GMAT Instructor V
Joined: 16 Aug 2015
Posts: 8025
GMAT 1: 760 Q51 V42 GPA: 3.82
Re: The Ultimate Q51 Guide [Expert Level]  [#permalink]

Show Tags

If x≠0, is x^2<|x|?

1) x<1
2) x>-1

==> If you modify the original condition and the question, from x^2<|x|?, |x|^2<|x|?, when you divide both sides by |x|, (Since |x|>0, the inequality sign doesn’t change after division) you get |x|<1?, and then -1<x<1?.

The answer is C.
_________________
Math Revolution GMAT Instructor V
Joined: 16 Aug 2015
Posts: 8025
GMAT 1: 760 Q51 V42 GPA: 3.82
Re: The Ultimate Q51 Guide [Expert Level]  [#permalink]

Show Tags

If n is the least common multiple of 18 and 60, which of the following can be the factor of n?

I. 24 II. 36 III. 45

A. Ⅰonly
B. Ⅱ only
C. Ⅲ only
D.Ⅰ& Ⅲ only
E. Ⅱ&Ⅲ only

==> You get 18=2(3^2) 60=(2^2)(3)(5), and since the least common multiple is the maximum value of the index, and you get n=(2^2)(3^2)(5).

Therefore, you get

I. 24=(2^3)(3) (X)
II. 36=(2^2)(32) (O)
III. 45=(3^2)(5) (O)

The answer is Ⅱ&Ⅲ, which is E.
_________________
Math Revolution GMAT Instructor V
Joined: 16 Aug 2015
Posts: 8025
GMAT 1: 760 Q51 V42 GPA: 3.82
Re: The Ultimate Q51 Guide [Expert Level]  [#permalink]

Show Tags

If p is the sum of all odd numbers greater than 0 but less than 50, and q is the sum of all even numbers greater than 0 but less than 50, what is the value of p-q?

A. -24
B. 0
C. 1
D. 24
E. 25

==> Since p=1+3+….+47+49, from q=2+4+…+46+48, the difference between 3+5+…+47+49 (part of p) and q=2+4+..+46+48 is 1 each, so there are 24. Since there is also +1 at the front of p, you get 24+1=25.

The answer is E.
_________________
Math Revolution GMAT Instructor V
Joined: 16 Aug 2015
Posts: 8025
GMAT 1: 760 Q51 V42 GPA: 3.82
Re: The Ultimate Q51 Guide [Expert Level]  [#permalink]

Show Tags

If set A={a,b,c,d,e}, what is the number of subsets that must include only 3 elements?

A. 8
B. 10
C. 12
D. 15
E. 18

==> You get 5C3=5C2=(5)(4)/2!=10.

The answer is b.
_________________
Math Revolution GMAT Instructor V
Joined: 16 Aug 2015
Posts: 8025
GMAT 1: 760 Q51 V42 GPA: 3.82
Re: The Ultimate Q51 Guide [Expert Level]  [#permalink]

Show Tags

When 2 dices are tossed, what is the probability that the 2 faced numbers have a difference of 3?

A. 1/9
B. 2/9
C. 1/3
D. 4/9
E. 1/6

==> Numerator:(6,3), (5,2), (4,1), (3,6), (2,5), (1,4). Denominator:6*6. Thus, you get 6/6*6=1/6.

The answer is E.
_________________
Math Revolution GMAT Instructor V
Joined: 16 Aug 2015
Posts: 8025
GMAT 1: 760 Q51 V42 GPA: 3.82
Re: The Ultimate Q51 Guide [Expert Level]  [#permalink]

Show Tags

If f(2x+3)=-6x, f(5)=?

A. -6
B. -3
C. -2
D. 3
E. 6

==> From 2x+3=5, you get x=1, and then you get f(5)=-6(1)=-6.

The answer is A.
_________________
Intern  B
Joined: 30 May 2014
Posts: 3
Re: The Ultimate Q51 Guide [Expert Level]  [#permalink]

Show Tags

MathRevolution wrote:
This is one of the most challenging types of the question that looks like a journal. This is a PS question that you should be familiar with.

It is well-known that the way to find out approximation value of a positive integer n’s square root is following;
1st approximation: select a positive integer "a" and n is divided by a.
2nd approximation: a positive integer n’s square root is the average (arithmetic mean) of a quotient and divisor.
What is the approximation positive integer n’s square root, in terms of a and n?
A. (a^2+n)/2a B. (a^2+n)/2 C. (a^2-n)/2a D. (a^2+n)/a E. (a^2+2n)/a
N=aQ, (a+Q)/2=(a+n/a)/2=(a^2+n)/2a

This type of questions looks very simple, but it is rather challenging. You should not underestimate the difficulty levels of PS questions (by the way this is a statistics problem).

MathRevolution , can you further expand on this problem? How did you reach the solution?
Math Revolution GMAT Instructor V
Joined: 16 Aug 2015
Posts: 8025
GMAT 1: 760 Q51 V42 GPA: 3.82
Re: The Ultimate Q51 Guide [Expert Level]  [#permalink]

Show Tags

If \$10,000 is invested at 8 percent annual interest, compounded semiannually, what is the balance after 5 year, in terms of dollars?

A. 10,000(1+ )^10
B. 10,000(1+0.08)^5
C. 10,000(1+0.08)
D. 10,000(1-0.08)^2
E. 10,000*1.08

==> if it is invested at 8 percent annual interest and is compounded semiannually, From
10,000(1+8%(1/2))^2*5= 10,000(1+ )^10 the answer is A

_________________
Manager  B
Joined: 04 May 2014
Posts: 151
Location: India
WE: Sales (Mutual Funds and Brokerage)
Re: The Ultimate Q51 Guide [Expert Level]  [#permalink]

Show Tags

How is it D? can you please elaborate. Should it not be E?

MathRevolution wrote:
Even for the mistake type 4 questions, they are becoming more complicated unlike simple questions in the past. For a question like the below, 1)=2), which is no and sufficient. Therefore, D is the answer.

(ex 3) If n is positive integer, is 3n+n2+1 not divisible by 3?
1) n is not multiple of 2
2) n is not multiple of 3

That is, questions are evolving like highly challenging questions, in which the mistake type 4 and 1 are combined. So, we should keep up with the evolving questions. In particular, integer questions are numerously given and you should carefully approach the questions, which will lead you to hit 51.
Math Revolution GMAT Instructor V
Joined: 16 Aug 2015
Posts: 8025
GMAT 1: 760 Q51 V42 GPA: 3.82
Re: The Ultimate Q51 Guide [Expert Level]  [#permalink]

Show Tags

3 robots can finish the same task in 6hrs, 7hrs, and 8hrs.What is the greatest part of the task that can be finished by two of these robots together in 1 hour?

A. 13/42
B. 11/42
C. 42/13
D. 42/11
E. 13/21

==> Assuming that A, B, and C finishes their tasks in 6hrs, 7hrs, and 8 hrs each, the work rate of A and B are good, and each finished 1/6 and 1/7, so you get 1/6+1/7=13/42.

The answer is A.
_________________
Intern  B
Joined: 21 Mar 2017
Posts: 49
Re: The Ultimate Q51 Guide [Expert Level]  [#permalink]

Show Tags

MathRevolution
Would you please share something so that I can learn how to spot Mistake Type/Trap Questions.?
Math Revolution GMAT Instructor V
Joined: 16 Aug 2015
Posts: 8025
GMAT 1: 760 Q51 V42 GPA: 3.82
Re: The Ultimate Q51 Guide [Expert Level]  [#permalink]

Show Tags

For x and y, what is the value of x?

1) (x-3)(x+y)=0
2) (x-3)(2x+y)=0

==> In the original condition, there are 2 variables (x,y) and in order to match the number of variables to the number of equations, there must be 2 equations. Since there is 1 for con 1) and 1 for con 2), C is most likely to be the answer. By solving con 1) and con 2), you get x=3, which is unique and sufficient. Therefore, the answer is C.
_________________
Math Revolution GMAT Instructor V
Joined: 16 Aug 2015
Posts: 8025
GMAT 1: 760 Q51 V42 GPA: 3.82
Re: The Ultimate Q51 Guide [Expert Level]  [#permalink]

Show Tags

1-c-d=?

1) c+d=-1
2) c=-1-d

==> In the original condition, there are 2 variables (c,d) and in order to match the number of variables to the number of equations, there must be 2 equations. Since there is 1 for con 1) and 1 for con 2), C is most likely to be the answer. By solving con 1) and con 2), you get con 1) = con 2), so both of them becomes c+d=-1, and 1-c-d=1-(c+d)=1-(-1)=2, hence it is unique and sufficient.

Therefore, the answer is D.
_________________ Re: The Ultimate Q51 Guide [Expert Level]   [#permalink] 11 Jul 2017, 18:04

Go to page   Previous    1  ...  11   12   13   14   15   16   17  ...  44    Next  [ 870 posts ]

Display posts from previous: Sort by

The Ultimate Q51 Guide [Expert Level]

 new topic post reply Question banks Downloads My Bookmarks Reviews Important topics

Moderator: DisciplinedPrep

 Powered by phpBB © phpBB Group | Emoji artwork provided by EmojiOne  