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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. Formula for the area of a circle?
2
A = pi(r^2)
23 - 29
413.03 / 10^4 (move the decimal point 4 places to the left)

2. What does the graph (x+2)^2 + (y+2)^2 = 9 look like?
A circle centered at -2 - -2 with radius 3.
(12/2) x (sqrt15 / sqrt5) = 6sqrt3
(a - b)^2
4:9. The ratio of the areas of two similar triangles equals the square of the ratio of the corresponding sides.

3. x^2 = 9. What is the value of x?
Cd
3 - -3
1.7
x^(2(4)) =x^8 = (x^4)^2

4. What is an isoceles triangle?
Two equal sides and two equal angles.
13
The overlapping sections.
Diameter(Pi)

5. Pi is a ratio of what to what?

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6. What are the irrational numbers?

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7. A brick with dimensions 10. 15 and 25 weighs 1.5 kg. A second brick (same density) has dimensions 12 - 18 - and 30. What is the weight of the second brick?
1
A 30-60-90 triangle.
2sqrt6
2.592 kg

8. Formula to calculate arc length?
A grouping of the members within a set based on a shared characteristic.
4:9. The ratio of the areas of two similar triangles equals the square of the ratio of the corresponding sides.
12.5%
Arc length = (n/360) x pi(2r) where n is the number of degrees.

9. 40 < all primes<50
When the function is not defined for all real numbers -; only a subset of the real numbers.
(n-2) x 180
A reflection about the axis.
41 - 43 - 47

10. How to determine percent decrease?
(amount of decrease/original price) x 100%
31 - 37
A reflection about the origin.
Area of the base X height = (pi)hr^2

11. 200 <_ x <_ 300. How many values of x are divisible by 5 & 8?
75:11
When we need to avoid having a zero in the denominator or avoid taking the square root of a number.
The longest arc between points A and B on a circle'S diameter.
3

12. What is the absolute value function?
G(x) = {x}
x^(6-3) = x^3
F(x + c)
The direction of the inequality is reversed.

13. (x^2)^4
3
(a - b)(a + b)
x^(2(4)) =x^8 = (x^4)^2
27^(-4)

14. 1/6 in percent?
A circle centered on the origin with radius 8.
Expressing a number as the product of a decimal between 1 and 10 - and a power of 10.
The set of elements found in both A and B.
16.6666%

15. 6w^2 - w - 15 = 0
Cd
61 - 67
3/2 - 5/3
F(x-c)

16. What are 'Supplementary angles?'
(a - b)(a + b)
Two angles whose sum is 180.
Pi is the ratio of a circle'S circumference to its diameter.
The union of A and B.

17. How many digits are there between the decimal point and the first even digit in the decimal equivalent of 1/[(2^8)(5^3)]
(p + q)/5
0
62.5%
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)

18. What is the name of set with a number of elements which cannot be counted?
27^(-4)
An infinite set.
13pi / 2
9 : 25

19. If the two sides of a triangle are unequal then the longer side...
x^(2(4)) =x^8 = (x^4)^2
2(pi)r^2 + 2(pi)rh
13pi / 2
Lies opposite the greater angle

20. What is the measure of an exterior angle of a regular pentagon?
Ax^2 + bx + c where a -b and c are constants and a /=0
Even
[(7+ sqrt93) /2] - [(7 - sqrt93) / 2]
72

21. What is the slope of a vertical line?

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22. Legs 6 - 8. Hypotenuse?
10
The interesection of A and B.
4:5
All numbers multiples of 1.

23. Simplify the expression (p^2 - q^2)/ -5(q - p)
An infinite set.
4a^2(b)
(p + q)/5
Use Pythagorean theorem twice. (Once across the surface and then a is the diagonal of surface and b is an edge).

24. 70 < all primes< 80
3
Yes - because you can factor out a perfect square (36). Sqrt(36 x 2) = sqrt36 X sqrt2 = 6sqrt2.
The sum of digits is divisible by 9.
71 - 73 - 79

25. 10^6 has how many zeroes?
(a - b)^2
6
1/a^6
N! / (k!)(n-k)!

26. Evaluate 4/11 + 11/12
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.
1 & 37/132
The empty set - 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)

27. 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?
Yes - because you can factor out a perfect square (36). Sqrt(36 x 2) = sqrt36 X sqrt2 = 6sqrt2.
75:11
N! / (k!)(n-k)!
Its negative reciprocal. (-b/a)

28. What are the smallest three prime numbers greater than 65?
67 - 71 - 73
90
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
x(x - y + 1)

29. 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?
y = 2x^2 - 3
The angle intersecting the circumference is always the largest angle - and is always 90 degrees.
6 : 1 : 2
(a + b)^2

30. What is the set of elements found in both A and B?
The interesection of A and B.
3
90
An arc is a portion of a circumference of a circle.

31. x^6 / x^3
6
x^(6-3) = x^3
A set with no members - denoted by a circle with a diagonal through it.
Expressing a number as the product of a decimal between 1 and 10 - and a power of 10.

32. 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.
130pi
90 degrees
Its divisible by 2 and by 3.
28. n = 8 - k = 2. n! / k!(n-k)!

33. If 8 schools are in a conference - how many games are played if each team plays each other exactly once?
From northeast - counterclockwise. I - II - III - IV
II
28. n = 8 - k = 2. n! / k!(n-k)!
6 : 1 : 2

34. In similar hexagons - the ratio of the areas is 16:25. What is the ratio of their corresponding sides?
4a^2(b)
12.5%
x= (1.2)(.8)lw
4:5

35. When does a function automatically have a restricted domain (2)?
(amount of increase/original price) x 100%
When we need to avoid having a zero in the denominator or avoid taking the square root of a number.
Relationship cannot be determined (what if x is negative?)
G(x) = {x}

36. Which quadrant is the upper right hand?
The greatest value minus the smallest.
The empty set - denoted by a circle with a diagonal through it.
A reflection about the axis.
I

37. Simplify the expression [(b^2 - c^2) / (b - c)]
Factors are few - multiples are many.
PEMDAS (Parentheses Exponents Multiplication/Division Addition/Subtraction)
x^(6-3) = x^3
(b + c)

38. From a box of 12 candles - you are to remove 5. How many different sets of 5 candles could you remove?
Ax^2 + bx + c where a -b and c are constants and a /=0
1
12! / 5!7! = 792
0

39. What is the name for a grouping of the members within a set based on a shared characteristic?
41 - 43 - 47
2^9 / 2 = 256
A subset.
0

40. There are 10 finalists for the school spelling bee. A first - second - and third place trophy will be awarded. In how many ways can the judges award the 3 prizes?
The point of intersection of the systems.
.0004809 X 10^11
10! / (10-3)! = 720
A grouping of the members within a set based on a shared characteristic.

41. What does the graph x^2 + y^2 = 64 look like?
Sector area = (n/360) X (pi)r^2
The shortest arc between points A and B on a circle'S diameter.
70
A circle centered on the origin with radius 8.

42. x^4 + x^7 =
52
4:5
2sqrt6
x^(4+7) = x^11

43. 60 < all primes <70
Move the decimal point to the right x places
87.5%
A central angle is an angle formed by 2 radii.
61 - 67

44. 5/8 in percent?
The overlapping sections.
62.5%
[(7+ sqrt93) /2] - [(7 - sqrt93) / 2]
1

45. What is the sum of the angles of a triangle?
11 - 13 - 17 - 19
F(x-c)
52
180 degrees

46. What is a chord of a circle?
Cd
A subset.
75:11
A chord is a line segment joining two points on a circle.

47. Simplify 4sqrt21 X 5sqrt2 / 10sqrt7
No - the input value has exactly one output.
The third side is greater than the difference and less than the sum.
10
2sqrt6

48. Describe the relationship between the graphs of x^2 and (1/2)x^2
1
Yes - because you can factor out a perfect square (36). Sqrt(36 x 2) = sqrt36 X sqrt2 = 6sqrt2.
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 second graph is less steep.

49. 5 bakeries sell an average of 300 muffins per bakery per day. If 2 stop making muffins but the total muffins sold stays the same - what is the average of muffins per bakery sold among the remaining?
500
12! / 5!7! = 792
13
x^(2(4)) =x^8 = (x^4)^2

50. What is an exterior angle?
x^(4+7) = x^11
$3 -500 in the 9% and $2 -500 in the 7%.
An expression with just one term (-6x - 2a^2)
An angle which is supplementary to an interior angle.