Overview of GMAT Math Question Types and Patterns on the GMAT

If f(n)=n(n+1), which of following is equal to f(8)/f(2)?
A. f(3) B. f(4) C. f(5) D. f(6) E. f(7)

==>You get f(8)/f(2)=8*9/2*3=4*3=f(3), so the answer is A.
Answer: A

In the x-y plane, there is line K, (x/a)+(y/b)=1. What is the y-intercept of line K?
1) a=b
2) b=5

==> If you modify the original condition and the question, the y-intercept is the value of y when x=0, so if you substitute x=0, from y/b=1, you get y=b, so you only need to know b. According to con 2), it is unique and sufficient.

Therefore, the answer is B.
Answer: B

A certain set X contains the number 20. Is the range of the numbers greater than 12?
1) The maximum of the set is 50
2) The set contains the number 25

==> In the original condition, from range=Max-min, there are 3 variables (r,M,m) and 1 equation (r=M-n), and in order to match the number of variables to the number of equations, there must be 2 more equations. Since there is 1 for con 1) and 1 for con 2), C is most likely to be the answer. However, for con 1), if Max=20, set X already includes 20, so the range is at least 50-20=30>12, hence it is always yes and sufficient.

Therefore, the answer is A.
Answer: A

When \(8^x=16\), x=?

A. \(\frac{2}{3}\)
B. \(\frac{3}{2}\)
C. \(\frac{3}{4}\)
D. \(\frac{4}{3}\)
E. \(\frac{4}{5}\)

==>From \(8^x=16\) to\(2^3^x=2^4\), you get \(3x=4, x=\frac{4}{3}\). Therefore, the answer is D.
Answer: D

If m and n are positive integers, what is the value of m+n?
1) m/n=3/5
2) The greatest common divisor of m and n is 5

==>In the original condition, there are 2 variables (m, n) for the right triangle, 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 M=3*5=13 and n=5*5=25, so m+n=25+15=40, hence it is unique and sufficient.

Therefore, the answer is C.
Answer: C

Dear MathRevolution & Bunuel, If \(x=0.5\) and \(y=1.5\), statement 1 still valid. Why D is not the answer?

MathRevolution

Could you please provide me information about which type of question comes under
1. DATA interpretation
2. Common Mistake Type (CMT)

What is the range of 30 consecutive even numbers?

A. 54 B. 56 C. 58 D. 60 E. 62

==> The number of consecutive numbers become (last-first/2)+1=(range/2)+1. In other words, from (range/2)+1=30, you get range/2=29, range=2(29)=58.

The answer is C.
Answer: C

Is -3<x<4?

1) -2<x<3
2) -4<x<4

==> In the original condition, there is 1 variable (x) and in order to match the number of variables to the number of equations, there must be 1 equation. Since there is 1 for con 1) and 1 for con 2), D is most likely to be the answer. For con 1), it is always yes, hence it is sufficient. For con 2), x=0 yes, but x=-3.5 no, hence it is not sufficient.

Therefore, the answer is A.
Answer: A

2x+3y=?

1) 2x+4y=3
2) 4x+6y=6

==> In the original condition, you get 2x+3y=(1/2)(4x+6y)=? From con 2), you get 4x+6y=6, hence it is unique and sufficient.

Therefore, the answer is B.
Answer: B

10+8÷3×6-2=?

A. 24
B. 34
C. 22
D. 12
E. 11

==> When calculating the numbers, even if there are no brackets, multiplication and division come first.
You get 10+8÷3×6-2=10+(8/3)6-2=10+16-2=24.

The answer is A.
Answer: A

If \(x^2=2x+1, x^3\)=？

A. 4x
B. 5x+2
C. 5x-1
D. 3x+2
E. 3x-2

==> \(x^3=x(x^2)=x(2x+1)=2x^2+x=2(2x+1)+x=5x+2\)
Answer: B

If a, b, and c are integers, is abc an even?

1) a+b is an even
2) b+c is an even

==> In the original condition, there are 3 variables (a,b,c) and in order to match the number of variables to the number of equations, there must be 3 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), if (a,b,c)=(1,1,1), you get a+b+c=1+1+1=3=odd, so no, but if (a,b,c)=(2,2,2), you get a+b+c=2+2+2=6=even, so yes, hence it is not sufficient.

The answer is E.
Answer: E

Which of the following is equal to
\(3^m7^{m-1}\)?


\(A. 3(21^m)\)
\(B. 7(21^m)\)
\(C. 3(21^{m-1})\)
\(D. 7(21^{m-1})\)
\(E. 21^{m-1}\)

==> From \(3^m7^m^-^1=3(3^m^-^1)(7^m^-^1)=3(3*7)^m^-^1=3(21^m^-^1)\), the answer is C.

Answer: C

Can someone please explain the solution of this question?

n=?
1) twice n equals to n+1
2) n times n equals to n
==> In the original condition, there is 1 variable (n) and in order to match the number of variables to the number of equations, there must be 1 equation. Since there is 1 for con 1) and 1 for con 2), D is most likely to be the answer.
For con 1), from 2n=n+1, you get n=1, hence sufficient.
For con 2), from \(n^2=n\) and \(n^2-n=0\), n(n-1)=0, you get n=0,1, hence it is not unique and not sufficient.

The answer is A.
Answer: A

If x and y are integers greater than 1 and x>y, what are the values of x and y?
1) x+y=13
2) xy=22

==> 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=11 and y=2, hence it is unique and sufficient. The answer is c. However, this is an integer question, one of the key questions, so you apply CMT 4(A).
For con 1), from (x,y)=(11,2),(10,3), it is not unique and not sufficient.
For con 2), you only get (x,y)=(2,11), hence it is unique.

Therefore, the answer is B, not C.
Answer: B