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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 the 80th percentile of the measurements is 72degrees - about how many measurments are between 69 degrees and 72 degrees? Round your answer to the nearest tenth
(6 x 2)(sqrt3 x sqrt5) = 12sqrt15
IV
2^9 / 2 = 256
18

2. Nine coins are tossed simultaneously. In how many of the outcomes will the fourth coin tossed show heads?
8
The shortest arc between points A and B on a circle'S diameter.
2^9 / 2 = 256
The interesection of A and B.

3. 20<all primes<30
413.03 / 10^4 (move the decimal point 4 places to the left)
4:5
1
23 - 29

4. 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.
6
An angle which is supplementary to an interior angle.
90 degrees
(12/2) x (sqrt15 / sqrt5) = 6sqrt3

5. Legs 6 - 8. Hypotenuse?
10
x^(2(4)) =x^8 = (x^4)^2
The steeper the slope.
It is a function defined by more than one equation - where each equation applies to a different part of the domain of the function.

6. Solve the quadratic equation ax^2 + bx + c= 0
Yes - like radicals can be added/subtracted.
x = [(-b)+/- (sqrt b^2 - 4ac)]/2a
Its negative reciprocal. (-b/a)
Its last two digits are divisible by 4.

7. Which quadrant is the upper left hand?
PEMDAS (Parentheses Exponents Multiplication/Division Addition/Subtraction)
52
An infinite set.
II

8. Formula to find a circle'S circumference from its radius?
C = 2(pi)r
72
72
Infinite.

9. Simplify the expression [(b^2 - c^2) / (b - c)]
x = [(-b)+/- (sqrt b^2 - 4ac)]/2a
(b + c)
The third side is greater than the difference and less than the sum.
4:5

10. What is the 'Range' of a function?
180 degrees
10! / (10-3)! = 720
The set of output values for a function.
Its divisible by 2 and by 3.

11. A cylinder has a surface area of 22pi. If the cylinder has a height of 10 - what is the radius?
62.5%
Two equal sides and two equal angles.
1
61 - 67

12. What is a central angle?
3 - -3
The angle intersecting the circumference is always the largest angle - and is always 90 degrees.
An angle which is supplementary to an interior angle.
A central angle is an angle formed by 2 radii.

13. What is a tangent?
x(x - y + 1)
Two angles whose sum is 90.
The set of input values for a function.
A tangent is a line that only touches one point on the circumference of a circle.

14. What is a chord of a circle?
71 - 73 - 79
1/a^6
A chord is a line segment joining two points on a circle.
No - only like radicals can be added.

15. Can you subtract 3sqrt4 from sqrt4?
All real numbers which can'T be expressed as a ratio of two integers - positive and negative (pi - -sqrt3)
72
9 & 6/7
Yes - like radicals can be added/subtracted.

16. The slope of a line perpendicular to (a/b)?
Its negative reciprocal. (-b/a)
The empty set - denoted by a circle with a diagonal through it.
The longest arc between points A and B on a circle'S diameter.
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

17. Suppose that the graph of f(x) is the result of sliding the graph of y=2x^2 down 3 units of spaces. What is the new equation?
Relationship cannot be determined (what if x is negative?)
4096
y = 2x^2 - 3
Members or elements

18. Evaluate 4/11 + 11/12
1 & 37/132
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)
Its negative reciprocal. (-b/a)
An arc is a portion of a circumference of a circle.

19. Can you simplify sqrt72?
13pi / 2
41 - 43 - 47
4:9. The ratio of the areas of two similar triangles equals the square of the ratio of the corresponding sides.
Yes - because you can factor out a perfect square (36). Sqrt(36 x 2) = sqrt36 X sqrt2 = 6sqrt2.

20. What does the graph x^2 + y^2 = 64 look like?
The interesection of A and B.
4:5
.0004809 X 10^11
A circle centered on the origin with radius 8.

21. Find the surface area of a cylinder with radius 3 and height 12.
No - the input value has exactly one output.
[(7+ sqrt93) /2] - [(7 - sqrt93) / 2]
From northeast - counterclockwise. I - II - III - IV
90pi

22. 6w^2 - w - 15 = 0
3/2 - 5/3
(n-2) x 180
10! / 3!(10-3)! = 120
41 - 43 - 47

23. Which quandrant is the lower right hand?
IV
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^(2(4)) =x^8 = (x^4)^2
All numbers multiples of 1.

24. What is the area of a regular hexagon with side 6?
x(x - y + 1)
54sqrt3. (divide the hexagon into 6 congruent equilateral triangles.
87.5%
3

25. 0^0
An arc is a portion of a circumference of a circle.
1
70
Undefined

26. (x^2)^4
All numbers which can be expressed as a ratio of two integers. (All integers and fractions.) (-2 - 1 - .25 - 1/2)
x^(2(4)) =x^8 = (x^4)^2
1
13

27. What is the set of elements found in both A and B?
500
y = 2x^2 - 3
The interesection of A and B.
16^8 - 64^5 = (4^3)^5 = 4^15 - 16^8=(4^2)^8 = 4^16

28. What is the ratio of the surface area of a cube with an edge of 10 to the surface area of a rectangular solid with dimensions 2 - 4 - and 6?
75:11
Area of the base X height = (pi)hr^2
12! / 5!7! = 792
G(x) = {x}

29. Pi is a ratio of what to what?

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30. How to determine percent decrease?
(amount of decrease/original price) x 100%
II
23 - 29
x^(2(4)) =x^8 = (x^4)^2

31. What is the sum of the angles of a triangle?
2sqrt6
Expressing a number as the product of a decimal between 1 and 10 - and a power of 10.
180 degrees
Even

32. What percent of 40 is 22?
2(pi)r^2 + 2(pi)rh
288 (8 9 4)
55%
1

33. What is the 'domain' of a function?
(a - b)(a + b)
All numbers which can be expressed as a ratio of two integers. (All integers and fractions.) (-2 - 1 - .25 - 1/2)
The set of input values for a function.
Factors are few - multiples are many.

34. In a regular polygon with n sides - the formula for the sum of interior angles
A reflection about the axis.
13
Relationship cannot be determined (what if x is negative?)
(n-2) x 180

35. What are congruent triangles?
1/(x^y)
I
Triangles with same measure and same side lengths.
The angle intersecting the circumference is always the largest angle - and is always 90 degrees.

36. 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)
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)
The greatest value minus the smallest.
(n-2) x 180
4.25 - 6 - 22

37. (12sqrt15) / (2sqrt5) =
1/(x^y)
(12/2) x (sqrt15 / sqrt5) = 6sqrt3
71 - 73 - 79
62.5%

38. Define an 'expression'.
The objects within a set.
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)
7 / 1000
6

39. A number is divisible by 6 if...
x = [(-b)+/- (sqrt b^2 - 4ac)]/2a
4725
Its divisible by 2 and by 3.
Its negative reciprocal. (-b/a)

40. 4.809 X 10^7 =
.0004809 X 10^11
x= (1.2)(.8)lw
1
7 / 1000

41. Which is greater? 27^(-4) or 9^(-8)
It is a function defined by more than one equation - where each equation applies to a different part of the domain of the function.
The graph of 3(x - 1)^2 is a translation (shift) of the graph one unit or space to the right.
27^(-4)
61 - 67

42. x^2 = 9. What is the value of x?
3 - -3
180
3
(a + b)^2

43. Can the input value of a function have more than one output value (i.e. x: y - y1)?
x(x - y + 1)
No - the input value has exactly one output.
$3 -500 in the 9% and $2 -500 in the 7%.
4:5

44. Hector invested $6000. Part was invested in account with 9% simple annual interest - and the rest in account with 7% simple annual interest. If he earned $490 in the first year of these investments - how much did he invest in each account?
Its last two digits are divisible by 4.
$3 -500 in the 9% and $2 -500 in the 7%.
The third side is greater than the difference and less than the sum.
72

45. The larger the absolute value of the slope...
Use Pythagorean theorem twice. (Once across the surface and then a is the diagonal of surface and b is an edge).
3 - -3
The steeper the slope.
G(x) = {x}

46. What is the third quartile of the following data set: 44 - 58 - 63 - 63 - 68 - 70 - 82
Angle/360 x (pi)r^2
70
4725
A tangent is a line that only touches one point on the circumference of a circle.

47. If 4500 is invested at a simple interest rate of 6% - what is the value of the investment after 10 months?
4725
1
y = 2x^2 - 3
Factors are few - multiples are many.

48. What is the ratio of the sides of an isosceles right triangle?
Infinite.
The curve opens upward and the vertex is the minimal point on the graph.
1:1:sqrt2
C = 2(pi)r

49. What is an exterior angle?
2.592 kg
A subset.
An angle which is supplementary to an interior angle.
(amount of increase/original price) x 100%

50. If an inequality is multiplied or divided by a negative number....
The direction of the inequality is reversed.
A central angle is an angle formed by 2 radii.
20.5
13