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Math Revolution GMAT Instructor
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Re: Math Revolution Approach (PS)
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17 Nov 2016, 04:14
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 Answer: E
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Math Revolution GMAT Instructor
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Re: Math Revolution Approach (PS)
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18 Nov 2016, 01:38
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
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21 Nov 2016, 02:02
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. Answer: D
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Math Revolution GMAT Instructor
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Re: Math Revolution Approach (PS)
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21 Nov 2016, 02:03
) 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
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Re: Math Revolution Approach (PS)
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23 Nov 2016, 01:20
Which of the following inequalities satisfy (x4) (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 (x4)(x+1)>0, you get x4>0, x+1>0 or x4<0, and x+1<0. Then, x4>0 and x+1>0 is x>4 and x>1, which becomes x>4, and x4<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. Answer: C
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Re: Math Revolution Approach (PS)
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24 Nov 2016, 02:46
A triangle’s area is S=\(\sqrt{( ((p) )(p) )(pc))}\), 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=\(\sqrt{√(p(pa)(pb)(pc))}\), it becomes S=\(\sqrt{(9*4*3*2)}\)=6√6. Therefore, the answer is C. Answer: C
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Math Revolution GMAT Instructor
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Re: Math Revolution Approach (PS)
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25 Nov 2016, 02:23
If (1+x)y=y(x1), 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(x1) on both sides, you get y+xy=yxy, hence y=y. In other words, you get 2y=0, hence y=0. The answer is B. Answer: B
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Re: Math Revolution Approach (PS)
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28 Nov 2016, 01:40
\((8^3 6^7)/3^7\) =? (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
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Re: Math Revolution Approach (PS)
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28 Nov 2016, 01:41
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+….+(2n1)=n 2, 1+3+…….(2*1001)=100 2 =10,000 is derived. Hence, the answer is D.
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Re: Math Revolution Approach (PS)
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30 Nov 2016, 03:10
If (1+x)y=y(x1), 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(x1) on both sides, you get y+xy=yxy, hence y=y. In other words, you get 2y=0, hence y=0. The answer is B. Answer: B
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01 Dec 2016, 02:01
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. Answer: D
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Re: Math Revolution Approach (PS)
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01 Dec 2016, 08:39
As per the question Line K is: y = ax + b The yintercept is y=b Hence, a = 4b Substituting to get the xintercept: 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



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02 Dec 2016, 01:54
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 (82), 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
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05 Dec 2016, 01:36
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. Answer: B
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Re: Math Revolution Approach (PS)
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05 Dec 2016, 01:38
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 ==> 1probability 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
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Re: Math Revolution Approach (PS)
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07 Dec 2016, 01:33
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)=21=1, and therefore the answer is D. Answer: D
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Math Revolution GMAT Instructor
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Re: Math Revolution Approach (PS)
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08 Dec 2016, 01:44
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
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Re: Math Revolution Approach (PS)
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09 Dec 2016, 01:48
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 \(x+y=5.\) Therefore, the answer is C. Answer: C
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Re: Math Revolution Approach (PS)
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12 Dec 2016, 01:17
If x1, 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 \((x1)^2+(x+6)^2=(x+7)^2\), you get \(x^22x+1+x^2+12x+36=x^2+14x+49\), and then when you simplify, you get \(x^24x12=0\). From \((x6)(x+2)=0\), \(x=6\), and therefore the answer is C. Answer: C
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Re: Math Revolution Approach (PS)
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12 Dec 2016, 01:20
m and n are positive integers. If an equation \(x^2+(m2)x(n2)=0\) 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 \((D)=b^24ac=0\). Therefore, you get \(D=(m2)^24*1*((n2))=0\), and \((m2)^2+8(n2)=0\). Only m=n=2 satisfies this because m and n are positive integers. Answer: C
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