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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. (6sqrt3) x (2sqrt5) =
A set with a number of elements which can be counted.
The angle intersecting the circumference is always the largest angle - and is always 90 degrees.
71 - 73 - 79
(6 x 2)(sqrt3 x sqrt5) = 12sqrt15

2. 10<all primes<20
Two angles whose sum is 90.
75:11
9 : 25
11 - 13 - 17 - 19

3. Circumference of a circle?
An expression with just one term (-6x - 2a^2)
Triangles with same measure and same side lengths.
1/2 times 7/3
Diameter(Pi)

4. Legs: 3 - 4. Hypotenuse?
5
Its divisible by 2 and by 3.
62.5%
An isosceles right triangle.

5. Formula to find a circle'S circumference from its diameter?
The set of output values for a function.
C = (pi)d
An expression with just one term (-6x - 2a^2)
A circle centered at -2 - -2 with radius 3.

6. What is the name of set with a number of elements which cannot be counted?
(n-2) x 180
The angle intersecting the circumference is always the largest angle - and is always 90 degrees.
An infinite set.
(amount of increase/original price) x 100%

7. 1/8 in percent?
A grouping of the members within a set based on a shared characteristic.
1
12.5%
54sqrt3. (divide the hexagon into 6 congruent equilateral triangles.

8. Simplify (a^2 + b)^2 - (a^2 - b)^2
4a^2(b)
(6 x 2)(sqrt3 x sqrt5) = 12sqrt15
Undefined
The set of output values for a function.

9. 4.809 X 10^7 =
.0004809 X 10^11
x= (1.2)(.8)lw
52
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)

10. If you have a set of n objects - but you only want to order k of them - what formula do you use to determine the number of permutations?
N! / (n-k)!
A circle centered on the origin with radius 8.
1
61 - 67

11. 5x^2 - 35x -55 = 0
[(7+ sqrt93) /2] - [(7 - sqrt93) / 2]
(n-2) x 180
An arc is a portion of a circumference of a circle.
(p + q)/5

12. 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?
90
75:11
13
The objects within a set.

13. 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?
Undefined - because we can'T divide by 0.
13
10! / (10-3)! = 720
6

14. What are the real numbers?
No - only like radicals can be added.
A grouping of the members within a set based on a shared characteristic.
72
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)

15. 0^0
61 - 67
A set with a number of elements which can be counted.
7 / 1000
Undefined

16. What is the area of a regular hexagon with side 6?
55%
54sqrt3. (divide the hexagon into 6 congruent equilateral triangles.
Diameter(Pi)
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. What is a major arc?

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18. Can the output value of a function have more than one input value?
Yes. [i.e. f(x) = x^2 - 1
Infinite.
The longest arc between points A and B on a circle'S diameter.
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.

19. For similar triangles - the ratio of their corresponding sides is 2:3. What is the ratio of their areas?
$3 -500 in the 9% and $2 -500 in the 7%.
4:9. The ratio of the areas of two similar triangles equals the square of the ratio of the corresponding sides.
500
Two equal sides and two equal angles.

20. (-1)^2 =
1
The direction of the inequality is reversed.
Its divisible by 2 and by 3.
Relationship cannot be determined (what if x is negative?)

21. If 4500 is invested at a simple interest rate of 6% - what is the value of the investment after 10 months?
10! / 3!(10-3)! = 120
4725
$11 -448
Triangles with same measure and same side lengths.

22. What is the maximum value for the function g(x) = (-2x^2) -1?
180
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
9 : 25

23. 1:sqrt3:2 is the ratio of the sides of what kind of triangle?
F(x) - c
The sum of digits is divisible by 9.
Divide by 100.
A 30-60-90 triangle.

24. Max and Min lengths for a side of a triangle?
The third side is greater than the difference and less than the sum.
Use Pythagorean theorem twice. (Once across the surface and then a is the diagonal of surface and b is an edge).
11 - 13 - 17 - 19
Indeterminable.

25. 3/8 in percent?
(6 x 2)(sqrt3 x sqrt5) = 12sqrt15
(p + q)/5
37.5%
(n-2) x 180

26. Is 0 even or odd?
The objects within a set.
52
1/(x^y)
Even

27. 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?
Angle/360 x (pi)r^2
2.592 kg
62.5%
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

28. A number is divisible by 9 if...
An infinite set.
62.5%
$3 -500 in the 9% and $2 -500 in the 7%.
The sum of digits is divisible by 9.

29. From a box of 12 candles - you are to remove 5. How many different sets of 5 candles could you remove?
72
1
A circle centered on the origin with radius 8.
12! / 5!7! = 792

30. Evaluate (4^3)^2
An isosceles right triangle.
x(x - y + 1)
54sqrt3. (divide the hexagon into 6 congruent equilateral triangles.
4096

31. 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?
52
F(x-c)
48
x(x - y + 1)

32. Legs 6 - 8. Hypotenuse?
10
y = (x + 5)/2
Expressing a number as the product of a decimal between 1 and 10 - and a power of 10.
3

33. When does a function automatically have a restricted domain (2)?
When we need to avoid having a zero in the denominator or avoid taking the square root of a number.
When the function is not defined for all real numbers -; only a subset of the real numbers.
A subset.
16.6666%

34. 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)
Angle/360 x 2(pi)r
A = I (1 + rt)
An isosceles right triangle.

35. 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?
4:5
N! / (k!)(n-k)!
F(x) + c
The sum of digits is divisible by 9.

36. Formula for the area of a circle?
5
G(x) = {x}
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
A = pi(r^2)

37. Formula of rectangle where l increases by 20% and w decreases by 20%
The shortest arc between points A and B on a circle'S diameter.
y = (x + 5)/2
18
x= (1.2)(.8)lw

38. What is the graph of f(x) shifted right c units or spaces?
F(x-c)
No - only like radicals can be added.
75:11
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

39. How many digits are there between the decimal point and the first even digit in the decimal equivalent of 1/[(2^8)(5^3)]
Two angles whose sum is 180.
0
1
83.333%

40. 413.03 x 10^(-4) =
413.03 / 10^4 (move the decimal point 4 places to the left)
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
Angle/360 x (pi)r^2
1

41. To convert a percent to a fraction....
From northeast - counterclockwise. I - II - III - IV
75:11
Divide by 100.
Factors are few - multiples are many.

42. 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?
2^9 / 2 = 256
83.333%
(a + b)^2
$3 -500 in the 9% and $2 -500 in the 7%.

43. What is a chord of a circle?
413.03 / 10^4 (move the decimal point 4 places to the left)
A chord is a line segment joining two points on a circle.
2sqrt6
2 & 3/7

44. What is the percent formula?
The steeper the slope.
Part = Percent X Whole
Members or elements
The overlapping sections.

45. A number is divisible by 6 if...
3
(a - b)^2
87.5%
Its divisible by 2 and by 3.

46. How many multiples does a given number have?
6 : 1 : 2
Two angles whose sum is 180.
Circumference = Diameter(pi). Use pythagorean theorem to find the diagonal of the square (the diameter).
Infinite.

47. For what values should the domain be restricted for the function f(x) = sqrt(x + 8)
Two equal sides and two equal angles.
Two angles whose sum is 90.
Undefined
8

48. x^(-y)=
...multiply by 100.
Yes - like radicals can be added/subtracted.
1/(x^y)
23 - 29

49. x^4 + x^7 =
x^(4+7) = x^11
x = [(-b)+/- (sqrt b^2 - 4ac)]/2a
1
0

50. What is the graph of f(x) shifted downward c units or spaces?
9 : 25
F(x) - c
7 / 1000
90 degrees