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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 10800 is invested at a simple interest rate of 4% - what is the value of the investment after 18 months?
(a + b)^2
(n-2) x 180
$11 -448
A circle centered on the origin with radius 8.

2. Formula of rectangle where l increases by 20% and w decreases by 20%
31 - 37
52
x= (1.2)(.8)lw
An angle which is supplementary to an interior angle.

3. 10<all primes<20
61 - 67
The angle intersecting the circumference is always the largest angle - and is always 90 degrees.
4:9. The ratio of the areas of two similar triangles equals the square of the ratio of the corresponding sides.
11 - 13 - 17 - 19

4. How to determine percent increase?
(amount of increase/original price) x 100%
54sqrt3. (divide the hexagon into 6 congruent equilateral triangles.
5 OR -5
12sqrt2

5. 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
An expression with just one term (-6x - 2a^2)
500
12.5%

6. 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?
(12/2) x (sqrt15 / sqrt5) = 6sqrt3
The curve opens downward and the vertex is the maximum point on the graph.
10! / (10-3)! = 720
III

7. 1/6 in percent?
16.6666%
28. n = 8 - k = 2. n! / k!(n-k)!
All numbers which can be expressed as a ratio of two integers. (All integers and fractions.) (-2 - 1 - .25 - 1/2)
4a^2(b)

8. To convert a decimal to a percent...
The curve opens upward and the vertex is the minimal point on the graph.
Divide by 100.
...multiply by 100.
Sqrt 12

9. Solve the quadratic equation ax^2 + bx + c= 0
x = [(-b)+/- (sqrt b^2 - 4ac)]/2a
70
F(x) + c
41 - 43 - 47

10. In a triangle inscribed inside a circle - where the diameter is one side of the triangle - which angle is largest?
130pi
The angle intersecting the circumference is always the largest angle - and is always 90 degrees.
4:5
Two equal sides and two equal angles.

11. Which is greater? 200x^295 or 10x^294?
61 - 67
Relationship cannot be determined (what if x is negative?)
Divide by 100.
Lies opposite the greater angle

12. Simplify (a^2 + b)^2 - (a^2 - b)^2
180 degrees
4a^2(b)
9 : 25
180

13. What is an isoceles triangle?
8
5
1
Two equal sides and two equal angles.

14. How to find the area of a sector?
3
N! / (k!)(n-k)!
20.5
Angle/360 x (pi)r^2

15. What is the 'Range' of a function?
The set of output values for a function.
52
16^8 - 64^5 = (4^3)^5 = 4^15 - 16^8=(4^2)^8 = 4^16
The empty set - denoted by a circle with a diagonal through it.

16. What is the third quartile of the following data set: 44 - 58 - 63 - 63 - 68 - 70 - 82
x^(2(4)) =x^8 = (x^4)^2
II
70
A 30-60-90 triangle.

17. How many multiples does a given number have?
No - the input value has exactly one output.
10
The longest arc between points A and B on a circle'S diameter.
Infinite.

18. 5/6 in percent?
83.333%
All real numbers which can'T be expressed as a ratio of two integers - positive and negative (pi - -sqrt3)
2^9 / 2 = 256
The objects within a set.

19. What is a chord of a circle?
28. n = 8 - k = 2. n! / k!(n-k)!
6
A 30-60-90 triangle.
A chord is a line segment joining two points on a circle.

20. What is the common monomial factor in the expression 4(c^3)d - (c^2)(d^2) + 2cd?
28. n = 8 - k = 2. n! / k!(n-k)!
12.5%
IV
Cd

21. What are the roots of the quadrinomial x^2 + 2x + 1?
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.
The sum of its digits is divisible by 3.
The two xes after factoring.
N! / (k!)(n-k)!

22. How to find the circumference of a circle which circumscribes a square?
Diameter(Pi)
(a - b)(a + b)
Circumference = Diameter(pi). Use pythagorean theorem to find the diagonal of the square (the diameter).
A reflection about the origin.

23. Define an 'expression'.
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)
(amount of increase/original price) x 100%
Pi is the ratio of a circle'S circumference to its diameter.
Arc length = (n/360) x pi(2r) where n is the number of degrees.

24. 1:sqrt3:2 is the ratio of the sides of what kind of triangle?
A 30-60-90 triangle.
Relationship cannot be determined (what if x is negative?)
16.6666%
3/2 - 5/3

25. 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?
N! / (k!)(n-k)!
2 & 3/7
(n-2) x 180
Use Pythagorean theorem twice. (Once across the surface and then a is the diagonal of surface and b is an edge).

26. a^2 - 2ab + b^2
2 & 3/7
Undefined - because we can'T divide by 0.
(a - b)^2
A central angle is an angle formed by 2 radii.

27. What are the irrational numbers?

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28. What is the 'Restricted domain of a function'?
10! / 3!(10-3)! = 120
72
When the function is not defined for all real numbers -; only a subset of the real numbers.
441000 = 1 10 10 10 21 * 21

29. a^2 - b^2
Yes. [i.e. f(x) = x^2 - 1
(a - b)(a + b)
72
1.7

30. What is the graph of f(x) shifted downward c units or spaces?
F(x) - c
The second graph is less steep.
...multiply by 100.
6

31. What are 'Supplementary angles?'
Even
5 OR -5
3sqrt4
Two angles whose sum is 180.

32. 20<all primes<30
Circumference = Diameter(pi). Use pythagorean theorem to find the diagonal of the square (the diameter).
23 - 29
6
Two angles whose sum is 180.

33. What is the ratio of the sides of a 30-60-90 triangle?
37.5%
Sector area = (n/360) X (pi)r^2
1:sqrt3:2
53 - 59

34. 10^6 has how many zeroes?
A set with no members - denoted by a circle with a diagonal through it.
6
31 - 37
3 - -3

35. 5x^2 - 35x -55 = 0
...multiply by 100.
Part = Percent X Whole
[(7+ sqrt93) /2] - [(7 - sqrt93) / 2]
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)

36. 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
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...
5
87.5%

37. What does the graph x^2 + y^2 = 64 look like?
1
A = I (1 + rt)
A circle centered on the origin with radius 8.
A reflection about the axis.

38. Which quadrant is the upper right hand?
4a^2(b)
72
No - only like radicals can be added.
I

39. sqrt 2(sqrt 6)=
A set with no members - denoted by a circle with a diagonal through it.
4:9. The ratio of the areas of two similar triangles equals the square of the ratio of the corresponding sides.
Sqrt 12
4725

40. A triangle is inscribed in a semi circle with legs 5 and 12. What is the circumfermence of the semicircle?
13pi / 2
The graph of 3(x - 1)^2 is a translation (shift) of the graph one unit or space to the right.
An angle which is supplementary to an interior angle.
The third side is greater than the difference and less than the sum.

41. Area of a triangle?
The longest arc between points A and B on a circle'S diameter.
Relationship cannot be determined (what if x is negative?)
(base*height) / 2
441000 = 1 10 10 10 21 * 21

42. a^0 =
A reflection about the origin.
1
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)
Yes - because you can factor out a perfect square (36). Sqrt(36 x 2) = sqrt36 X sqrt2 = 6sqrt2.

43. Factor a^2 + 2ab + b^2
The set of output values for a function.
(a + b)^2
A reflection about the axis.
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

44. For what values should the domain be restricted for the function f(x) = sqrt(x + 8)
The two xes after factoring.
8
53 - 59
48

45. What is the side length of an equilateral triangle with altitude 6?
Lies opposite the greater angle
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 union of A and B.
Indeterminable.

46. Formula to calculate arc length?
Arc length = (n/360) x pi(2r) where n is the number of degrees.
90 degrees
4096
3sqrt4

47. A number is divisible by 3 if ...
$11 -448
The sum of its digits is divisible by 3.
A central angle is an angle formed by 2 radii.
All numbers multiples of 1.

48. What is a tangent?
A tangent is a line that only touches one point on the circumference of a circle.
5 OR -5
Arc length = (n/360) x pi(2r) where n is the number of degrees.
Yes. [i.e. f(x) = x^2 - 1

49. 1:1:sqrt2 is the ratio of the sides of what kind of triangle?
... the square of the ratios of the corresponding sides.
Its divisible by 2 and by 3.
An isosceles right triangle.
3/2 - 5/3

50. (-1)^3 =
Use Pythagorean theorem twice. (Once across the surface and then a is the diagonal of surface and b is an edge).
(amount of increase/original price) x 100%
The interesection of A and B.
1