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# Math Revolution Approach (PS)

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Math Revolution GMAT Instructor
Joined: 16 Aug 2015
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Re: Math Revolution Approach (PS)  [#permalink]

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17 Nov 2016, 03:14
If x is a prime number, which of the following cannot be an integer?
A. x/2 B. 5x/3 C. 3x/7 D. 15x/6 E. x/6

==> A. x=2, B. x=3, C. x=7, D. x=2. E. impossible
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MathRevolution: Finish GMAT Quant Section with 10 minutes to spare
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"Only $149 for 3 month Online Course" "Free Resources-30 day online access & Diagnostic Test" "Unlimited Access to over 120 free video lessons - try it yourself" Math Revolution GMAT Instructor Joined: 16 Aug 2015 Posts: 6815 GMAT 1: 760 Q51 V42 GPA: 3.82 Re: Math Revolution Approach (PS) [#permalink] ### Show Tags 18 Nov 2016, 00:38 U and T can produce 10,000 units in x hours when working together at their constant rates. If U can produce 10,000 units in 4x/3 hours alone at the constant rate, in how many hours can T produce 10,000 units alone at the constant rate, in terms of x? A. 5x/2 B. 4x C. 2x D. x E. x/2 ==> In case of work rate questions, if it is “together and alone”, you solve it reciprocally. In other words, if you assume the time it takes for T to produce 10,000 units alone as t hrs, you get t=4x from 1/(4x/3)+1/t=1/x. Therefore, B is the answer. Answer: B _________________ MathRevolution: Finish GMAT Quant Section with 10 minutes to spare The one-and-only World’s First Variable Approach for DS and IVY Approach for PS with ease, speed and accuracy. "Only$149 for 3 month Online Course"
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Math Revolution GMAT Instructor
Joined: 16 Aug 2015
Posts: 6815
GMAT 1: 760 Q51 V42
GPA: 3.82
Re: Math Revolution Approach (PS)  [#permalink]

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21 Nov 2016, 01:02
If n is the product of 3 consecutive integers, which of the following must be true?

I. a multiple of 2 II. a multiple of 3 III. a multiple of 4

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

==> The product of 3 consecutive integers always become the multiple of 6, because the product always contains 3 and 2. Thus, in this question, it always becomes the multiple of 6 that contain 3 and 2, I and II are the answer. Therefore, the answer is D. III does not work because it becomes 1*2*3*=6, hence it cannot be the multiple of 4.

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"Only $149 for 3 month Online Course" "Free Resources-30 day online access & Diagnostic Test" "Unlimited Access to over 120 free video lessons - try it yourself" Math Revolution GMAT Instructor Joined: 16 Aug 2015 Posts: 6815 GMAT 1: 760 Q51 V42 GPA: 3.82 Re: Math Revolution Approach (PS) [#permalink] ### Show Tags 21 Nov 2016, 01:03 ) If Tom goes y miles in x hours, how many miles does he go per minute, in terms of x and y? A. 60x/y B. y/60x C. 60y/x D. x/60y E. 60xy ==> Tom goes y miles: x hours, so from y miles: x (60) minutes = (y/60x) miles: 1 minute, the answer is B. Answer: B _________________ MathRevolution: Finish GMAT Quant Section with 10 minutes to spare The one-and-only World’s First Variable Approach for DS and IVY Approach for PS with ease, speed and accuracy. "Only$149 for 3 month Online Course"
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Math Revolution GMAT Instructor
Joined: 16 Aug 2015
Posts: 6815
GMAT 1: 760 Q51 V42
GPA: 3.82
Re: Math Revolution Approach (PS)  [#permalink]

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23 Nov 2016, 00:20
Which of the following inequalities satisfy (x-4) (x+1) >0?
A. -1<x<4 B. -4<x<1 C. x<-1, 4<x D. x<-4, 1<x E. -1<x<1

==> From (x-4)(x+1)>0, you get x-4>0, x+1>0 or x-4<0, and x+1<0. Then, x-4>0 and x+1>0 is x>4 and x>-1, which becomes x>4, and x-4<0 and x+1<0 becomes x<-1 from x<4 and x<-1, hence the answer is x<-1 or 4<X. Therefore, the answer is C.
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MathRevolution: Finish GMAT Quant Section with 10 minutes to spare
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"Only $149 for 3 month Online Course" "Free Resources-30 day online access & Diagnostic Test" "Unlimited Access to over 120 free video lessons - try it yourself" Math Revolution GMAT Instructor Joined: 16 Aug 2015 Posts: 6815 GMAT 1: 760 Q51 V42 GPA: 3.82 Re: Math Revolution Approach (PS) [#permalink] ### Show Tags 24 Nov 2016, 01:46 A triangle’s area is S=$$\sqrt{( ((p-) )(p-) )(p-c))}$$, where a, b and c are the three side lengths of the triangle and p=(a+b+c)/2. When a=5, b=6 and c=7, what is the area of the triangle? A. 4√6 B. 5√6 C. 6√6 D. 7√6 E. 8√6 ==> If you substitute p=(5+6+7)/2=9 into S=$$\sqrt{√(p(p-a)(p-b)(p-c))}$$, it becomes S=$$\sqrt{(9*4*3*2)}$$=6√6. Therefore, the answer is C. Answer: C _________________ MathRevolution: Finish GMAT Quant Section with 10 minutes to spare The one-and-only World’s First Variable Approach for DS and IVY Approach for PS with ease, speed and accuracy. "Only$149 for 3 month Online Course"
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Math Revolution GMAT Instructor
Joined: 16 Aug 2015
Posts: 6815
GMAT 1: 760 Q51 V42
GPA: 3.82
Re: Math Revolution Approach (PS)  [#permalink]

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25 Nov 2016, 01:23
If (1+x)y=y(x-1), which of the following must be true?

(A) x=-1 or y=0

(B) y=0

(C) x=1 or y=1

(D) x=-1 or y=-1

(E) x=0

=> If you expand (1+x)y=y(x-1) on both sides, you get y+xy=yx-y, hence y=-y. In other words, you get 2y=0, hence y=0.

_________________

MathRevolution: Finish GMAT Quant Section with 10 minutes to spare
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"Only $149 for 3 month Online Course" "Free Resources-30 day online access & Diagnostic Test" "Unlimited Access to over 120 free video lessons - try it yourself" Math Revolution GMAT Instructor Joined: 16 Aug 2015 Posts: 6815 GMAT 1: 760 Q51 V42 GPA: 3.82 Re: Math Revolution Approach (PS) [#permalink] ### Show Tags 28 Nov 2016, 00:40 $$(8^3 6^7)/3^7$$ =? (A) 214 (B) 215 (C) 216 (D) 217 (E) 218 $$(8^3 6^7)/3^7 =(2^9 〖(2∗3)〗^7)/3^7 =(2^9 2^7 3^7)/3^7 =2^9*2^7=2^16$$. The answer is C. Answer: C _________________ MathRevolution: Finish GMAT Quant Section with 10 minutes to spare The one-and-only World’s First Variable Approach for DS and IVY Approach for PS with ease, speed and accuracy. "Only$149 for 3 month Online Course"
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Math Revolution GMAT Instructor
Joined: 16 Aug 2015
Posts: 6815
GMAT 1: 760 Q51 V42
GPA: 3.82
Re: Math Revolution Approach (PS)  [#permalink]

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28 Nov 2016, 00:41
What is the sum of the first 100 positive odd numbers?

A. 5,000 B. 7,500 C. 8,000 D. 10,000 E. 12,000

==> Since 1+3+5+….+(2n-1)=n 2, 1+3+…….(2*100-1)=100 2 =10,000 is derived.
_________________

MathRevolution: Finish GMAT Quant Section with 10 minutes to spare
The one-and-only World’s First Variable Approach for DS and IVY Approach for PS with ease, speed and accuracy.
"Only $149 for 3 month Online Course" "Free Resources-30 day online access & Diagnostic Test" "Unlimited Access to over 120 free video lessons - try it yourself" Math Revolution GMAT Instructor Joined: 16 Aug 2015 Posts: 6815 GMAT 1: 760 Q51 V42 GPA: 3.82 Re: Math Revolution Approach (PS) [#permalink] ### Show Tags 30 Nov 2016, 02:10 If (1+x)y=y(x-1), which of the following must be true? (A) x=-1 or y=0 (B) y=0 (C) x=1 or y=1 (D) x=-1 or y=-1 (E) x=0 =>If you expand (1+x)y=y(x-1) on both sides, you get y+xy=yx-y, hence y=-y. In other words, you get 2y=0, hence y=0. The answer is B. Answer: B _________________ MathRevolution: Finish GMAT Quant Section with 10 minutes to spare The one-and-only World’s First Variable Approach for DS and IVY Approach for PS with ease, speed and accuracy. "Only$149 for 3 month Online Course"
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Math Revolution GMAT Instructor
Joined: 16 Aug 2015
Posts: 6815
GMAT 1: 760 Q51 V42
GPA: 3.82
Re: Math Revolution Approach (PS)  [#permalink]

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01 Dec 2016, 01:01
If $$n=2^5*3^4*5^3*7^2*11$$, how many factors of n are there?

A. 180 B. 360 C. 540 D. 720 E. 810

==> The number of factors become (5+1)(4+1)(3+1)(2+1)(1+1)=720, and therefore the answer is D.

_________________

MathRevolution: Finish GMAT Quant Section with 10 minutes to spare
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"Only $149 for 3 month Online Course" "Free Resources-30 day online access & Diagnostic Test" "Unlimited Access to over 120 free video lessons - try it yourself" Intern Joined: 26 Jun 2016 Posts: 3 Re: Math Revolution Approach (PS) [#permalink] ### Show Tags 01 Dec 2016, 07:39 As per the question Line K is: y = ax + b The y-intercept is y=b Hence, a = 4b Substituting to get the x-intercept: 0=ax+b > 0=4b x + b > -b=4bx > x=-b/4b=-1/4 Answer C Sent from my iPhone using GMAT Club Forum mobile app Math Revolution GMAT Instructor Joined: 16 Aug 2015 Posts: 6815 GMAT 1: 760 Q51 V42 GPA: 3.82 Re: Math Revolution Approach (PS) [#permalink] ### Show Tags 02 Dec 2016, 00:54 What is the measurement of one inner angle of the regular octagon? A.$$115^o$$ B. $$120^o$$ C. $$125^o$$ D. $$130^o$$ E. $$135^o$$ ==> An octagon’s total number of triangle is (8-2), so the total inner angle is 6*$$180^o$$=$$1,480^o$$, and since it is an octagon, if you divide by 8, it becomes $$1,480^o$$/8=$$135^o$$r. Therefore, the answer is E. Answer: E _________________ MathRevolution: Finish GMAT Quant Section with 10 minutes to spare The one-and-only World’s First Variable Approach for DS and IVY Approach for PS with ease, speed and accuracy. "Only$149 for 3 month Online Course"
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Math Revolution GMAT Instructor
Joined: 16 Aug 2015
Posts: 6815
GMAT 1: 760 Q51 V42
GPA: 3.82
Re: Math Revolution Approach (PS)  [#permalink]

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05 Dec 2016, 00:36
The standard deviation of which of the following is equivalent to that of {m, r, p, n}?
A. {2m, 2r, 2p, 2n}
B. {m+2, r+2, p+2, n+2}
C. {|m|, |r|, |p|, |n|}
D. {1/m, 1/r, 1/p, 1/n}
E. $${m^2, r^2, p^2, n^2}$$

==> Parallel translation doesn’t change the standard deviation. Therefore, the answer is B. In other words, each elements of B moves +2 in parallel, so the standard deviation doesn’t change.

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"Only $149 for 3 month Online Course" "Free Resources-30 day online access & Diagnostic Test" "Unlimited Access to over 120 free video lessons - try it yourself" Math Revolution GMAT Instructor Joined: 16 Aug 2015 Posts: 6815 GMAT 1: 760 Q51 V42 GPA: 3.82 Re: Math Revolution Approach (PS) [#permalink] ### Show Tags 05 Dec 2016, 00:38 There are 5 females and 3 males. If 3 people are selected randomly, what is the probability of at least one male getting selected from the people? A. 2/3 B. 3/31 C. 23/28 D. 25/28 E. 27/28 ==> 1-probability of not selecting one male=1-(probability of 3 selected people being all females)=1-(5C3/8C3)=1-(5/28)=23/28. Therefore, the answer is C. Answer: C _________________ MathRevolution: Finish GMAT Quant Section with 10 minutes to spare The one-and-only World’s First Variable Approach for DS and IVY Approach for PS with ease, speed and accuracy. "Only$149 for 3 month Online Course"
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Math Revolution GMAT Instructor
Joined: 16 Aug 2015
Posts: 6815
GMAT 1: 760 Q51 V42
GPA: 3.82
Re: Math Revolution Approach (PS)  [#permalink]

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07 Dec 2016, 00:33
G(x) is the greatest integer less than or equal to x and L(x) is the smallest integer greater than or equal to x. Which of the following can be the value of L(1.1)-G(1.1)?

A. -2 B. -1 C. 0 D. 1 E. 2

==> You get L(1.1)-G(1.1)=2-1=1, and therefore the answer is D.

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"Only $149 for 3 month Online Course" "Free Resources-30 day online access & Diagnostic Test" "Unlimited Access to over 120 free video lessons - try it yourself" Math Revolution GMAT Instructor Joined: 16 Aug 2015 Posts: 6815 GMAT 1: 760 Q51 V42 GPA: 3.82 Re: Math Revolution Approach (PS) [#permalink] ### Show Tags 08 Dec 2016, 00:44 What is the remainder when $$3^5^0$$ is divided by 4? A. 0 B. 1 C. 2 D. 3 E. -1 ==> The units digit of $$3^n$$ is the repetition of $$3-->9-->7--->1-->3-->9-->7-->1$$, so you get $$50=4*12+2$$. Thus, from $$3^5^0=3^4^*^1^2^+^2$$ --> $$~3^2=~9$$, the units digit becomes 9, and if you divide it by 4, from $$9=4*2+1$$, the remainder becomes 1. Therefore, the answer is B. Answer: B _________________ MathRevolution: Finish GMAT Quant Section with 10 minutes to spare The one-and-only World’s First Variable Approach for DS and IVY Approach for PS with ease, speed and accuracy. "Only$149 for 3 month Online Course"
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Math Revolution GMAT Instructor
Joined: 16 Aug 2015
Posts: 6815
GMAT 1: 760 Q51 V42
GPA: 3.82
Re: Math Revolution Approach (PS)  [#permalink]

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09 Dec 2016, 00:48
If $$2^x2^y=32, x+y$$=?

A. 3
B. 4
C. 5
D. 6
E. 7

==> From $$2^x2^y=2^x^+^y= 32=2^5$$, you get $$x+y=5.$$

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The one-and-only World’s First Variable Approach for DS and IVY Approach for PS with ease, speed and accuracy.
"Only $149 for 3 month Online Course" "Free Resources-30 day online access & Diagnostic Test" "Unlimited Access to over 120 free video lessons - try it yourself" Math Revolution GMAT Instructor Joined: 16 Aug 2015 Posts: 6815 GMAT 1: 760 Q51 V42 GPA: 3.82 Re: Math Revolution Approach (PS) [#permalink] ### Show Tags 12 Dec 2016, 00:17 If x-1, x+6, x+7 are 3 side lengths of a right triangle, what is the value of x? A. 4 B. 5 C. 6 D. 7 E. 8 ==> According to the Pythagorean Theorem, if you expand $$(x-1)^2+(x+6)^2=(x+7)^2$$, you get $$x^2-2x+1+x^2+12x+36=x^2+14x+49$$, and then when you simplify, you get $$x^2-4x-12=0$$. From $$(x-6)(x+2)=0$$, $$x=6$$, and therefore the answer is C. Answer: C _________________ MathRevolution: Finish GMAT Quant Section with 10 minutes to spare The one-and-only World’s First Variable Approach for DS and IVY Approach for PS with ease, speed and accuracy. "Only$149 for 3 month Online Course"
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Math Revolution GMAT Instructor
Joined: 16 Aug 2015
Posts: 6815
GMAT 1: 760 Q51 V42
GPA: 3.82
Re: Math Revolution Approach (PS)  [#permalink]

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12 Dec 2016, 00:20
m and n are positive integers. If an equation $$x^2+(m-2)x-(n-2)=0$$ has only one root, what is the value of mn?

==> For ax^2+bx+c=0 to have only one root, it needs to become discriminant $$(D)=b^2-4ac=0$$.
Therefore, you get $$D=(m-2)^2-4*1*(-(n-2))=0$$, and $$(m-2)^2+8(n-2)=0$$.
Only m=n=2 satisfies this because m and n are positive integers.

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Re: Math Revolution Approach (PS) &nbs [#permalink] 12 Dec 2016, 00:20

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# Math Revolution Approach (PS)

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