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GRE Math: Common Errors

Subjects : gre, math

Instructions:

Answer 50 questions in 15 minutes.
If you are not ready to take this test, you can study here.
Match each statement with the correct term.
Don't refresh. All questions and answers are randomly picked and ordered every time you load a test.

This is a study tool. The 3 wrong answers for each question are randomly chosen from answers to other questions. So, you might find at times the answers obvious, but you will see it re-enforces your understanding as you take the test each time.

1. If r - t - s & u are distinct - consecutive prime numbers - less than 31 - which of the following could be an average of them (4 - 4.25 - 6 - 9 - 24 - 22 - 24)
12! / 5!7! = 792
The steeper the slope.
10
4.25 - 6 - 22

2. How to determine percent increase?
(amount of increase/original price) x 100%
Expressing a number as the product of a decimal between 1 and 10 - and a power of 10.
12! / 5!7! = 792
4.25 - 6 - 22

3. If you have a set of n objects - but you only want to order k of them - what formula do you use to determine the number of permutations?
From northeast - counterclockwise. I - II - III - IV
N! / (n-k)!
Yes. [i.e. f(x) = x^2 - 1
The overlapping sections.

4. Surface area for a cylinder?
A circle centered at -2 - -2 with radius 3.
11 - 13 - 17 - 19
2(pi)r^2 + 2(pi)rh
F(x-c)

5. How to find the diagonal of a rectangular solid?
13
Use Pythagorean theorem twice. (Once across the surface and then a is the diagonal of surface and b is an edge).
41 - 43 - 47
All the numbers on the number line (negative - rational - irrational - decimal - integer). All the numbers on the GRE are real. (-2 - 1 - .25 - 1/2 - pi)

6. Factor x^2 - xy + x.
2(pi)r^2 + 2(pi)rh
x(x - y + 1)
Move the decimal point to the right x places
Diameter(Pi)

7. If the two sides of a triangle are unequal then the longer side...
Circumference = Diameter(pi). Use pythagorean theorem to find the diagonal of the square (the diameter).
A circle centered on the origin with radius 8.
x = [(-b)+/- (sqrt b^2 - 4ac)]/2a
Lies opposite the greater angle

8. 3/8 in percent?
Part = Percent X Whole
2(pi)r^2 + 2(pi)rh
37.5%
4sqrt3. The triangle can be divided into two equal 30-60-90 triangles with side 6 as the side in which 6 = xsqrt3. So x =2sqrt3...

9. (x^2)^4
The empty set - denoted by a circle with a diagonal through it.
All numbers multiples of 1.
An algebraic expression is a combination of one of more terms. Terms in an expression are separated by either addition or subtraction signs. (3xy - 4ab - -5cd - x^2 + x - 1)
x^(2(4)) =x^8 = (x^4)^2

10. The ratio of the areas of two similar polygons is ...
52
5 OR -5
9 & 6/7
... the square of the ratios of the corresponding sides.

11. Evaluate 3& 2/7 / 1/3
9 & 6/7
6
The two xes after factoring.
(n-2) x 180

12. 2sqrt4 + sqrt4 =
16^8 - 64^5 = (4^3)^5 = 4^15 - 16^8=(4^2)^8 = 4^16
71 - 73 - 79
16.6666%
3sqrt4

13. What is the sum of the angles of a triangle?
...multiply by 100.
3 - -3
180 degrees
Its last two digits are divisible by 4.

14. x^4 + x^7 =
(6 x 2)(sqrt3 x sqrt5) = 12sqrt15
An infinite set.
No - the input value has exactly one output.
x^(4+7) = x^11

15. What is a finite set?
Part = Percent X Whole
N! / (n-k)!
1.7
A set with a number of elements which can be counted.

16. What are congruent triangles?
Triangles with same measure and same side lengths.
13pi / 2
Its last two digits are divisible by 4.
1/2 times 7/3

17. Formula to calculate arc length?
0
$11 -448
Arc length = (n/360) x pi(2r) where n is the number of degrees.
A term is a numerical constant or the product (or quotient) of a numerical constant and one or more variables. (3x - 4x^2 and 2a/c)

18. Describe the relationship between the graphs of x^2 and (1/2)x^2
The second graph is less steep.
An angle which is supplementary to an interior angle.
441000 = 1 10 10 10 21 * 21
y = (x + 5)/2

19. Convert 0.7% to a fraction.
1
2 & 3/7
7 / 1000
Indeterminable.

20. 0^0
The curve opens upward and the vertex is the minimal point on the graph.
4725
28. n = 8 - k = 2. n! / k!(n-k)!
Undefined

21. Formula to find a circle'S circumference from its radius?
The angle intersecting the circumference is always the largest angle - and is always 90 degrees.
C = 2(pi)r
II
1/2 times 7/3

22. 10^6 has how many zeroes?
6
441000 = 1 10 10 10 21 * 21
All numbers which can be expressed as a ratio of two integers. (All integers and fractions.) (-2 - 1 - .25 - 1/2)
12! / 5!7! = 792

23. Write 10 -843 X 10^7 in scientific notation
1.0843 X 10^11
3 - -3
16.6666%
Arc length = (n/360) x pi(2r) where n is the number of degrees.

24. A number is divisible by 6 if...
G(x) = {x}
Its divisible by 2 and by 3.
3sqrt4
1.7

25. Factor a^2 + 2ab + b^2
The steeper the slope.
(p + q)/5
(a + b)^2
The sum of digits is divisible by 9.

26. Is 0 even or odd?
Yes - because you can factor out a perfect square (36). Sqrt(36 x 2) = sqrt36 X sqrt2 = 6sqrt2.
A term is a numerical constant or the product (or quotient) of a numerical constant and one or more variables. (3x - 4x^2 and 2a/c)
Arc length = (n/360) x pi(2r) where n is the number of degrees.
Even

27. Legs 6 - 8. Hypotenuse?
18
Sector area = (n/360) X (pi)r^2
10
10! / 3!(10-3)! = 120

28. Describe the relationship between 3x^2 and 3(x - 1)^2
F(x-c)
The third side is greater than the difference and less than the sum.
The graph of 3(x - 1)^2 is a translation (shift) of the graph one unit or space to the right.
1.7

29. What is the set of elements which can be found in either A or B?
(12/2) x (sqrt15 / sqrt5) = 6sqrt3
The union of A and B.
90 degrees
A chord is a line segment joining two points on a circle.

30. 70 < all primes< 80
71 - 73 - 79
1
6
Two equal sides and two equal angles.

31. What is the intersection of A and B?
An expression with just one term (-6x - 2a^2)
52
The union of A and B.
The set of elements found in both A and B.

32. Simplify the expression [(b^2 - c^2) / (b - c)]
20.5
62.5%
(b + c)
Divide by 100.

33. x^(-y)=
Angle/360 x 2(pi)r
1/(x^y)
13pi / 2
x= (1.2)(.8)lw

34. Simplify 9^(1/2) X 4^3 X 2^(-6)?
The graph of 3(x - 1)^2 is a translation (shift) of the graph one unit or space to the right.
A = I (1 + rt)
The curve opens downward and the vertex is the maximum point on the graph.
3

35. 200 <_ x <_ 300. How many values of x are divisible by 5 & 8?
III
5
2 & 3/7
3

36. 413.03 x 10^(-4) =
413.03 / 10^4 (move the decimal point 4 places to the left)
(n-2) x 180
11 - 13 - 17 - 19
Move the decimal point to the right x places

37. If 4500 is invested at a simple interest rate of 6% - what is the value of the investment after 10 months?
8
4sqrt3. The triangle can be divided into two equal 30-60-90 triangles with side 6 as the side in which 6 = xsqrt3. So x =2sqrt3...
Members or elements
4725

38. a^2 - b^2
A set with no members - denoted by a circle with a diagonal through it.
All the numbers on the number line (negative - rational - irrational - decimal - integer). All the numbers on the GRE are real. (-2 - 1 - .25 - 1/2 - pi)
x^(6-3) = x^3
(a - b)(a + b)

39. What are the real numbers?
A central angle is an angle formed by 2 radii.
12sqrt2
The shortest arc between points A and B on a circle'S diameter.
All the numbers on the number line (negative - rational - irrational - decimal - integer). All the numbers on the GRE are real. (-2 - 1 - .25 - 1/2 - pi)

40. What are the integers?
Factors are few - multiples are many.
.0004809 X 10^11
Expressing a number as the product of a decimal between 1 and 10 - and a power of 10.
All numbers multiples of 1.

41. Formula of rectangle where l increases by 20% and w decreases by 20%
2.4. We calculate the area (6) and then turn the triangle on its side and use x as the height to calculate again. (5x)/2=6
4:9. The ratio of the areas of two similar triangles equals the square of the ratio of the corresponding sides.
9 : 25
x= (1.2)(.8)lw

42. The four angles around a point measure y - 2y - 35 and 55 respectively. What is the value of y?
5 OR -5
180
90
An arc is a portion of a circumference of a circle.

43. What is the 'union' of A and B?
C = (pi)d
C = 2(pi)r
The set of elements which can be found in either A or B.
4.25 - 6 - 22

44. What is a parabola?
10! / (10-3)! = 720
Cd
Ax^2 + bx + c where a -b and c are constants and a /=0
72

45. When the 'a' in a parabola is positive....
12! / 5!7! = 792
The curve opens upward and the vertex is the minimal point on the graph.
[(7+ sqrt93) /2] - [(7 - sqrt93) / 2]
Angle/360 x 2(pi)r

46. How many multiples does a given number have?
1
Infinite.
23 - 29
F(x) - c

47. For what values should the domain be restricted for the function f(x) = sqrt(x + 8)
6
8
... the square of the ratios of the corresponding sides.
18

48. 5/6 in percent?
(a + b)^2
83.333%
Triangles with same measure and same side lengths.
A= I (1 + (r/c))^tC - where I is the investment - C is the number of times compounded annually - and t is the number of years.

49. 1/8 in percent?
Members or elements
12.5%
Circumference = Diameter(pi). Use pythagorean theorem to find the diagonal of the square (the diameter).
Indeterminable.

50. Suppose you have a set of n objects - and you want to select k of them - but the order doesn'T matter. What formula do you use to determine the number of combinations of n objects taken k at a time?
[(7+ sqrt93) /2] - [(7 - sqrt93) / 2]
(n-2) x 180
... the square of the ratios of the corresponding sides.
N! / (k!)(n-k)!