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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. From a box of 12 candles - you are to remove 5. How many different sets of 5 candles could you remove?
12! / 5!7! = 792
Its divisible by 2 and by 3.
130pi
4.25 - 6 - 22

2. What are congruent triangles?
Its last two digits are divisible by 4.
12sqrt2
Triangles with same measure and same side lengths.
The third side is greater than the difference and less than the sum.

3. How to find the diagonal of a rectangular solid?
The empty set - denoted by a circle with a diagonal through it.
Use Pythagorean theorem twice. (Once across the surface and then a is the diagonal of surface and b is an edge).
9 & 6/7
1.0843 X 10^11

4. What is the sum of the angles of a triangle?
The steeper the slope.
500
180 degrees
The interesection of A and B.

5. 7/8 in percent?
87.5%
Its negative reciprocal. (-b/a)
x^(4+7) = x^11
Factors are few - multiples are many.

6. When the 'a' in a parabola is positive....
4a^2(b)
II
The curve opens upward and the vertex is the minimal point on the graph.
9 : 25

7. What is a chord of a circle?
The set of input values for a function.
y = 2x^2 - 3
Expressing a number as the product of a decimal between 1 and 10 - and a power of 10.
A chord is a line segment joining two points on a circle.

8. Describe the relationship between 3x^2 and 3(x - 1)^2
87.5%
PEMDAS (Parentheses Exponents Multiplication/Division Addition/Subtraction)
The graph of 3(x - 1)^2 is a translation (shift) of the graph one unit or space to the right.
An expression with just one term (-6x - 2a^2)

9. 1/6 in percent?
III
16.6666%
The angle intersecting the circumference is always the largest angle - and is always 90 degrees.
A central angle is an angle formed by 2 radii.

10. 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?
A grouping of the members within a set based on a shared characteristic.
6
$3 -500 in the 9% and $2 -500 in the 7%.
x^(4+7) = x^11

11. In a regular polygon with n sides - the formula for the sum of interior angles
Its negative reciprocal. (-b/a)
An infinite set.
(n-2) x 180
3sqrt4

12. 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?
500
13pi / 2
5
N! / (k!)(n-k)!

13. If 10800 is invested at a simple interest rate of 4% - what is the value of the investment after 18 months?
$11 -448
10
3 - -3
Its divisible by 2 and by 3.

14. How to determine percent decrease?
(amount of decrease/original price) x 100%
Its divisible by 2 and by 3.
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...
The set of elements which can be found in either A or B.

15. 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.
90 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)
1
180

16. Can the output value of a function have more than one input value?
Indeterminable.
1
A reflection about the axis.
Yes. [i.e. f(x) = x^2 - 1

17. The larger the absolute value of the slope...
F(x-c)
Its last two digits are divisible by 4.
The steeper the slope.
180

18. What is the area of a regular hexagon with side 6?
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
54sqrt3. (divide the hexagon into 6 congruent equilateral triangles.
Indeterminable.
53 - 59

19. What is a major arc?

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20. Formula to find a circle'S circumference from its radius?
Move the decimal point to the right x places
C = 2(pi)r
A reflection about the axis.
5

21. If a=-1 and b=3 - what is the value of (4(a^3)(b^2) - 12(a^2)(b^5)) / (16(a^3)(b^2))?
The overlapping sections.
The sum of digits is divisible by 9.
(a - b)(a + b)
20.5

22. 2sqrt4 + sqrt4 =
y = (x + 5)/2
F(x) + c
3sqrt4
No - the input value has exactly one output.

23. How to find the area of a sector?
(a - b)(a + b)
[(7+ sqrt93) /2] - [(7 - sqrt93) / 2]
4725
Angle/360 x (pi)r^2

24. What is the set of elements found in both A and B?
3/2 - 5/3
An isosceles right triangle.
The interesection of A and B.
x = [(-b)+/- (sqrt b^2 - 4ac)]/2a

25. What are the rational numbers?
The third side is greater than the difference and less than the sum.
20.5
All numbers which can be expressed as a ratio of two integers. (All integers and fractions.) (-2 - 1 - .25 - 1/2)
Two angles whose sum is 90.

26. If 4500 is invested at a simple interest rate of 6% - what is the value of the investment after 10 months?
16.6666%
1
4725
52

27. Simplify 4sqrt21 X 5sqrt2 / 10sqrt7
Diameter(Pi)
2sqrt6
5 OR -5
F(x) - c

28. 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
The union of A and B.
18
An infinite set.
The angle intersecting the circumference is always the largest angle - and is always 90 degrees.

29. Simplify 9^(1/2) X 4^3 X 2^(-6)?
The steeper the slope.
$11 -448
3
Angle/360 x 2(pi)r

30. Which is greater? 200x^295 or 10x^294?
Relationship cannot be determined (what if x is negative?)
62.5%
A circle centered at -2 - -2 with radius 3.
A = I (1 + rt)

31. 30< all primes<40
3sqrt4
F(x) - c
31 - 37
$11 -448

32. What percent of 40 is 22?
A reflection about the axis.
55%
6
Factors are few - multiples are many.

33. Surface area for a cylinder?
...multiply by 100.
2 & 3/7
2(pi)r^2 + 2(pi)rh
90 degrees

34. Which is greater? 27^(-4) or 9^(-8)
27^(-4)
Two equal sides and two equal angles.
62.5%
Undefined

35. 60 < all primes <70
75:11
Its divisible by 2 and by 3.
23 - 29
61 - 67

36. Find the surface area of a cylinder with radius 3 and height 12.
90pi
Arc length = (n/360) x pi(2r) where n is the number of degrees.
9 : 25
No - the input value has exactly one output.

37. Which is greater? 64^5 or 16^8
16^8 - 64^5 = (4^3)^5 = 4^15 - 16^8=(4^2)^8 = 4^16
23 - 29
Even
III

38. 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)?
y = (x + 5)/2
(base*height) / 2
Diameter(Pi)
The interesection of A and B.

39. 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?
(6 x 2)(sqrt3 x sqrt5) = 12sqrt15
3 - -3
52
All numbers which can be expressed as a ratio of two integers. (All integers and fractions.) (-2 - 1 - .25 - 1/2)

40. A number is divisible by 4 is...
F(x + c)
The point of intersection of the systems.
The union of A and B.
Its last two digits are divisible by 4.

41. What is the ratio of the sides of an isosceles right triangle?
1:sqrt3:2
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...
1:1:sqrt2
12sqrt2

42. Can the input value of a function have more than one output value (i.e. x: y - y1)?
12.5%
No - the input value has exactly one output.
The curve opens upward and the vertex is the minimal point on the graph.
180 degrees

43. Formula to calculate arc length?
.0004809 X 10^11
A reflection about the origin.
12sqrt2
Arc length = (n/360) x pi(2r) where n is the number of degrees.

44. If 8 schools are in a conference - how many games are played if each team plays each other exactly once?
The steeper the slope.
Cd
Its negative reciprocal. (-b/a)
28. n = 8 - k = 2. n! / k!(n-k)!

45. In a triangle where the two legs are 4 and 3 - what is the value of a line directly intersecting the middle coming from the meeting point of the two legs?
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
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(x - y + 1)
1

46. 5/6 in percent?
5
90
A chord is a line segment joining two points on a circle.
83.333%

47. Write 10 -843 X 10^7 in scientific notation
The direction of the inequality is reversed.
1.0843 X 10^11
A chord is a line segment joining two points on a circle.
28. n = 8 - k = 2. n! / k!(n-k)!

48. Employee X is paid 19.50 per hour no matter how many a week. Employee Y earns 18 for the first 40 and 1.5 the hourly wage for every hour after that. If both earned the same amount and worked the same in one week - how many did each work?
An infinite set.
True
70
48

49. (6sqrt3) x (2sqrt5) =
A set with no members - denoted by a circle with a diagonal through it.
(6 x 2)(sqrt3 x sqrt5) = 12sqrt15
A 30-60-90 triangle.
I

50. 200 <_ x <_ 300. How many values of x are divisible by 5 & 8?
3sqrt4
16^8 - 64^5 = (4^3)^5 = 4^15 - 16^8=(4^2)^8 = 4^16
It is a function defined by more than one equation - where each equation applies to a different part of the domain of the function.
3