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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. To multiply a number by 10^x
The empty set - denoted by a circle with a diagonal through it.
Angle/360 x (pi)r^2
y = 2x^2 - 3
Move the decimal point to the right x places

2. What are congruent triangles?
3
Triangles with same measure and same side lengths.
A 30-60-90 triangle.
Area of the base X height = (pi)hr^2

3. Order of quadrants:
Angle/360 x 2(pi)r
y = 2x^2 - 3
From northeast - counterclockwise. I - II - III - IV
1

4. 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?
10! / 3!(10-3)! = 120
4096
2
52

5. Formula for the area of a circle?
It is a function defined by more than one equation - where each equation applies to a different part of the domain of the function.
4725
10! / (10-3)! = 720
A = pi(r^2)

6. 1:sqrt3:2 is the ratio of the sides of what kind of triangle?
A 30-60-90 triangle.
The third side is greater than the difference and less than the sum.
441000 = 1 10 10 10 21 * 21
1:1:sqrt2

7. (x^2)^4
x^(2(4)) =x^8 = (x^4)^2
Two angles whose sum is 180.
13pi / 2
12sqrt2

8. The perimeter of a square is 48 inches. The length of its diagonal is:
12sqrt2
x= (1.2)(.8)lw
y = (x + 5)/2
4096

9. In a triangle inscribed inside a circle - where the diameter is one side of the triangle - which angle is largest?
1/a^6
67 - 71 - 73
The angle intersecting the circumference is always the largest angle - and is always 90 degrees.
F(x) + c

10. When does a function automatically have a restricted domain (2)?
Angle/360 x (pi)r^2
When we need to avoid having a zero in the denominator or avoid taking the square root of a number.
7 / 1000
An angle which is supplementary to an interior angle.

11. What is the slope of a horizontal line?
The direction of the inequality is reversed.
0
Infinite.
x^(6-3) = x^3

12. a^2 - b^2 =
G(x) = {x}
(a - b)(a + b)
$11 -448
Two angles whose sum is 180.

13. Convert 0.7% to a fraction.
61 - 67
Lies opposite the greater angle
7 / 1000
72

14. Legs: 3 - 4. Hypotenuse?
67 - 71 - 73
5
(6 x 2)(sqrt3 x sqrt5) = 12sqrt15
61 - 67

15. From a box of 12 candles - you are to remove 5. How many different sets of 5 candles could you remove?
Area of the base X height = (pi)hr^2
10
1 & 37/132
12! / 5!7! = 792

16. Max and Min lengths for a side of a triangle?
The sum of digits is divisible by 9.
The third side is greater than the difference and less than the sum.
13
A set with a number of elements which can be counted.

17. A triangle is inscribed in a semi circle with legs 5 and 12. What is the circumfermence of the semicircle?
13pi / 2
No - only like radicals can be added.
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)
y = (x + 5)/2

18. 10^6 has how many zeroes?
20.5
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)
A = I (1 + rt)

19. When the 'a' in a parabola is positive....
28. n = 8 - k = 2. n! / k!(n-k)!
II
The curve opens upward and the vertex is the minimal point on the graph.
All numbers multiples of 1.

20. For similar triangles - the ratio of their corresponding sides is 2:3. What is the ratio of their areas?
180 degrees
G(x) = {x}
70
4:9. The ratio of the areas of two similar triangles equals the square of the ratio of the corresponding sides.

21. 40 < all primes<50
61 - 67
10! / 3!(10-3)! = 120
41 - 43 - 47
441000 = 1 10 10 10 21 * 21

22. What does the graph (x+2)^2 + (y+2)^2 = 9 look like?
x(x - y + 1)
A circle centered at -2 - -2 with radius 3.
Circumference = Diameter(pi). Use pythagorean theorem to find the diagonal of the square (the diameter).
An expression with just one term (-6x - 2a^2)

23. What is an isoceles triangle?
62.5%
52
Two equal sides and two equal angles.
F(x + c)

24. 1/6 in percent?
9 & 6/7
16.6666%
(a - b)(a + b)
x^(2(4)) =x^8 = (x^4)^2

25. How many sides does a hexagon have?
1/2 times 7/3
4096
6
All real numbers which can'T be expressed as a ratio of two integers - positive and negative (pi - -sqrt3)

26. What does the graph x^2 + y^2 = 64 look like?
An infinite set.
27^(-4)
4:9. The ratio of the areas of two similar triangles equals the square of the ratio of the corresponding sides.
A circle centered on the origin with radius 8.

27. Legs 5 - 12. Hypotenuse?
The curve opens upward and the vertex is the minimal point on the graph.
A reflection about the origin.
13
Its last two digits are divisible by 4.

28. What is the graph of f(x) shifted upward c units or spaces?
The point of intersection of the systems.
Pi is the ratio of a circle'S circumference to its diameter.
F(x) + c
(amount of increase/original price) x 100%

29. How many 3-digit positive integers are even and do not contain the digit 4?
413.03 / 10^4 (move the decimal point 4 places to the left)
288 (8 9 4)
1 & 37/132
Cd

30. What is a set with no members called?
A = pi(r^2)
The empty set - denoted by a circle with a diagonal through it.
x = [(-b)+/- (sqrt b^2 - 4ac)]/2a
A set with no members - denoted by a circle with a diagonal through it.

31. 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)?
70
90 degrees
y = (x + 5)/2
The second graph is less steep.

32. Can you simplify sqrt72?
83.333%
1
The longest arc between points A and B on a circle'S diameter.
Yes - because you can factor out a perfect square (36). Sqrt(36 x 2) = sqrt36 X sqrt2 = 6sqrt2.

33. 4.809 X 10^7 =
Two angles whose sum is 180.
.0004809 X 10^11
The set of output values for a function.
1.7

34. If 8 schools are in a conference - how many games are played if each team plays each other exactly once?
28. n = 8 - k = 2. n! / k!(n-k)!
70
(a + b)^2
54sqrt3. (divide the hexagon into 6 congruent equilateral triangles.

35. What is the 'Solution' for a set of inequalities.
2
Arc length = (n/360) x pi(2r) where n is the number of degrees.
The overlapping sections.
C = 2(pi)r

36. x^2 = 9. What is the value of x?
Undefined - because we can'T divide by 0.
(b + c)
3 - -3
Move the decimal point to the right x places

37. T or F? Given d -e &f =/ 0 - [(d^3)e(f^5)] / 2d(e^3) / [3(d^2)(e^3)(f^7)] / [6(e^5)(f^2)]?
The shortest arc between points A and B on a circle'S diameter.
True
The interesection of A and B.
71 - 73 - 79

38. What is the 'union' of A and B?
1
x= (1.2)(.8)lw
Sector area = (n/360) X (pi)r^2
The set of elements which can be found in either A or B.

39. Which quadrant is the upper left hand?
Angle/360 x (pi)r^2
Infinite.
II
23 - 29

40. Which quandrant is the lower right hand?
An expression with just one term (-6x - 2a^2)
71 - 73 - 79
IV
(a + b)^2

41. What is a piecewise equation?
x^(4+7) = x^11
1
It is a function defined by more than one equation - where each equation applies to a different part of the domain of the function.
87.5%

42. How many digits are there between the decimal point and the first even digit in the decimal equivalent of 1/[(2^8)(5^3)]
The two xes after factoring.
3/2 - 5/3
y = (x + 5)/2
0

43. 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?
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)
N! / (k!)(n-k)!
1
12sqrt2

44. Formula for the area of a sector of a circle?
[(7+ sqrt93) /2] - [(7 - sqrt93) / 2]
(n-2) x 180
3/2 - 5/3
Sector area = (n/360) X (pi)r^2

45. 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
y = (x + 5)/2
3 - -3
C = 2(pi)r
18

46. What are the real numbers?
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)
The overlapping sections.
(p + q)/5

47. What is the ratio of the sides of an isosceles right triangle?
All real numbers which can'T be expressed as a ratio of two integers - positive and negative (pi - -sqrt3)
1:1:sqrt2
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
75:11

48. (12sqrt15) / (2sqrt5) =
(12/2) x (sqrt15 / sqrt5) = 6sqrt3
75:11
12.5%
F(x) + c

49. A number is divisible by 3 if ...
The sum of its digits is divisible by 3.
1:1:sqrt2
The interesection of A and B.
83.333%

50. 70 < all primes< 80
71 - 73 - 79
1.7
1:sqrt3:2
A reflection about the axis.