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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. What are 'Supplementary angles?'
Two angles whose sum is 180.
A chord is a line segment joining two points on a circle.
41 - 43 - 47
II

2. What is the 'Solution' for a system of linear equations?
13
10! / 3!(10-3)! = 120
The point of intersection of the systems.
28. n = 8 - k = 2. n! / k!(n-k)!

3. Can you simplify sqrt72?
Yes - because you can factor out a perfect square (36). Sqrt(36 x 2) = sqrt36 X sqrt2 = 6sqrt2.
8
13
A central angle is an angle formed by 2 radii.

4. When does a function automatically have a restricted domain (2)?
...multiply by 100.
83.333%
67 - 71 - 73
When we need to avoid having a zero in the denominator or avoid taking the square root of a number.

5. Formula of rectangle where l increases by 20% and w decreases by 20%
An expression with just one term (-6x - 2a^2)
x= (1.2)(.8)lw
(6 x 2)(sqrt3 x sqrt5) = 12sqrt15
3/2 - 5/3

6. In a triangle inscribed inside a circle - where the diameter is one side of the triangle - which angle is largest?
6
The angle intersecting the circumference is always the largest angle - and is always 90 degrees.
x^(4+7) = x^11
48

7. Number of degrees in a triangle
(a - b)(a + b)
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)
180
288 (8 9 4)

8. Is 0 even or odd?
180
3
Even
20.5

9. What is the absolute value function?
Yes. [i.e. f(x) = x^2 - 1
G(x) = {x}
A central angle is an angle formed by 2 radii.
The interesection of A and B.

10. Area of a triangle?
A subset.
(base*height) / 2
62.5%
Arc length = (n/360) x pi(2r) where n is the number of degrees.

11. 20<all primes<30
83.333%
23 - 29
A set with no members - denoted by a circle with a diagonal through it.
A circle centered at -2 - -2 with radius 3.

12. sqrt 2(sqrt 6)=
61 - 67
41 - 43 - 47
Sqrt 12
10! / (10-3)! = 720

13. What is the third quartile of the following data set: 44 - 58 - 63 - 63 - 68 - 70 - 82
III
70
A set with a number of elements which can be counted.
16^8 - 64^5 = (4^3)^5 = 4^15 - 16^8=(4^2)^8 = 4^16

14. What is it called when a point is reflected to the quadrant opposite it (i.e. I to III or II to IV)?
71 - 73 - 79
53 - 59
A reflection about the origin.
A circle centered on the origin with radius 8.

15. Define an 'expression'.
The direction of the inequality is reversed.
1/2 times 7/3
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)
1 & 37/132

16. What is a finite set?
6
Undefined - because we can'T divide by 0.
Undefined
A set with a number of elements which can be counted.

17. What is the sum of the angles of a triangle?
Two angles whose sum is 90.
Area of the base X height = (pi)hr^2
180 degrees
(b + c)

18. What is a central angle?
180 degrees
A central angle is an angle formed by 2 radii.
62.5%
(12/2) x (sqrt15 / sqrt5) = 6sqrt3

19. Evaluate and write as a mixed number: 2/7 - 3/21 + 2 & 4/14
Move the decimal point to the right x places
12sqrt2
2 & 3/7
An arc is a portion of a circumference of a circle.

20. x^6 / x^3
F(x + c)
x^(6-3) = x^3
7 / 1000
C = (pi)d

21. What is the coefficient of the x^2 term in the product of (x + 1)(x + 2)(x -1)?
31 - 37
4:5
2
The set of elements which can be found in either A or B.

22. (6sqrt3) x (2sqrt5) =
16^8 - 64^5 = (4^3)^5 = 4^15 - 16^8=(4^2)^8 = 4^16
Yes. [i.e. f(x) = x^2 - 1
(6 x 2)(sqrt3 x sqrt5) = 12sqrt15
52

23. Suppose that the graph of f(x) is the result of stretching y=x + 5 away from the x-axis by a factor of 2. What is the new equation for the graph f(x)?
4:5
16.6666%
The empty set - denoted by a circle with a diagonal through it.
y = (x + 5)/2

24. 70 < all primes< 80
F(x) + c
The set of elements found in both A and B.
71 - 73 - 79
12! / 5!7! = 792

25. If an inequality is multiplied or divided by a negative number....
The greatest value minus the smallest.
The direction of the inequality is reversed.
The curve opens downward and the vertex is the maximum point on the graph.
Use Pythagorean theorem twice. (Once across the surface and then a is the diagonal of surface and b is an edge).

26. How many sides does a hexagon have?
An expression with just one term (-6x - 2a^2)
6
(12/2) x (sqrt15 / sqrt5) = 6sqrt3
All numbers multiples of 1.

27. The number of degrees in the largest angle of a triangle inscribed in a circle - in which the diameter of the circle is one side of the triangle.
A reflection about the origin.
Yes - because you can factor out a perfect square (36). Sqrt(36 x 2) = sqrt36 X sqrt2 = 6sqrt2.
90 degrees
x= (1.2)(.8)lw

28. What is the set of elements found in both A and B?
The interesection of A and B.
90pi
(amount of decrease/original price) x 100%
C = 2(pi)r

29. How many digits are there between the decimal point and the first even digit in the decimal equivalent of 1/[(2^8)(5^3)]
0
A set with a number of elements which can be counted.
71 - 73 - 79
(base*height) / 2

30. Evaluate 4/11 + 11/12
1 & 37/132
0
Sqrt 12
90pi

31. 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?
A tangent is a line that only touches one point on the circumference of a circle.
180 degrees
N! / (n-k)!
Angle/360 x 2(pi)r

32. For what values should the domain be restricted for the function f(x) = sqrt(x + 8)
52
When the function is not defined for all real numbers -; only a subset of the real numbers.
1/2 times 7/3
8

33. Can you add sqrt 3 and sqrt 5?
No - only like radicals can be added.
The objects within a set.
A = I (1 + rt)
180

34. What is the 'Restricted domain of a function'?
Pi is the ratio of a circle'S circumference to its diameter.
Its last two digits are divisible by 4.
.0004809 X 10^11
When the function is not defined for all real numbers -; only a subset of the real numbers.

35. Formula to calculate arc length?
It is a function defined by more than one equation - where each equation applies to a different part of the domain of the function.
Sector area = (n/360) X (pi)r^2
.0004809 X 10^11
Arc length = (n/360) x pi(2r) where n is the number of degrees.

36. 5/8 in percent?
The set of elements which can be found in either A or B.
62.5%
A circle centered at -2 - -2 with radius 3.
(a + b)^2

37. To convert a decimal to a percent...
F(x + c)
(p + q)/5
27^(-4)
...multiply by 100.

38. What is the intersection of A and B?
67 - 71 - 73
The interesection of A and B.
The set of elements found in both A and B.
(a - b)^2

39. Define a 'monomial'
An expression with just one term (-6x - 2a^2)
.0004809 X 10^11
(a + b)^2
1:sqrt3:2

40. Formula for the area of a sector of a circle?
2.592 kg
288 (8 9 4)
A grouping of the members within a set based on a shared characteristic.
Sector area = (n/360) X (pi)r^2

41. The slope of a line perpendicular to (a/b)?
Its negative reciprocal. (-b/a)
3sqrt4
A tangent is a line that only touches one point on the circumference of a circle.
10! / (10-3)! = 720

42. A number is divisible by 9 if...
Indeterminable.
A = I (1 + rt)
The sum of digits is divisible by 9.
A grouping of the members within a set based on a shared characteristic.

43. When the 'a' in the parabola is negative...
A = I (1 + rt)
G(x) = {x}
The curve opens downward and the vertex is the maximum point on the graph.
3

44. What is the 'Range' of a series of numbers?
The greatest value minus the smallest.
The interesection of A and B.
75:11
I

45. a^0 =
61 - 67
5
72
1

46. 1/8 in percent?
12.5%
All numbers which can be expressed as a ratio of two integers. (All integers and fractions.) (-2 - 1 - .25 - 1/2)
4725
Factors are few - multiples are many.

47. When the 'a' in a parabola is positive....
The second graph is less steep.
The curve opens upward and the vertex is the minimal point on the graph.
12.5%
413.03 / 10^4 (move the decimal point 4 places to the left)

48. If Madagascar'S exports totaled 1.3 billion in 2009 - and 4% came from China - what was the value in millions of the country'S exports to China?
70
1/(x^y)
The longest arc between points A and B on a circle'S diameter.
52

49. To multiply a number by 10^x
1
(b + c)
Move the decimal point to the right x places
288 (8 9 4)

50. How to determine percent decrease?
4725
Move the decimal point to the right x places
Sector area = (n/360) X (pi)r^2
(amount of decrease/original price) x 100%