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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. What is a chord of a circle?
A chord is a line segment joining two points on a circle.
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)
Relationship cannot be determined (what if x is negative?)

2. To multiply a number by 10^x
Move the decimal point to the right x places
11 - 13 - 17 - 19
(a - b)(a + b)
1

3. What is the 'Range' of a function?
10! / 3!(10-3)! = 120
The set of output values for a function.
The interesection of A and B.
12.5%

4. 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
x = [(-b)+/- (sqrt b^2 - 4ac)]/2a
10
2(pi)r^2 + 2(pi)rh

5. 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?
1
413.03 / 10^4 (move the decimal point 4 places to the left)
A tangent is a line that only touches one point on the circumference of a circle.
N! / (n-k)!

6. 40 < all primes<50
41 - 43 - 47
All numbers which can be expressed as a ratio of two integers. (All integers and fractions.) (-2 - 1 - .25 - 1/2)
x = [(-b)+/- (sqrt b^2 - 4ac)]/2a
The angle intersecting the circumference is always the largest angle - and is always 90 degrees.

7. If 4500 is invested at a simple interest rate of 6% - what is the value of the investment after 10 months?
6
Factors are few - multiples are many.
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.
4725

8. Define an 'expression'.
75:11
F(x) - c
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)
1

9. What is a minor arc?

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10. The slope of a line perpendicular to (a/b)?
The steeper the slope.
5
...multiply by 100.
Its negative reciprocal. (-b/a)

11. Number of degrees in a triangle
Lies opposite the greater angle
180
x= (1.2)(.8)lw
The steeper the slope.

12. (x^2)^4
28. n = 8 - k = 2. n! / k!(n-k)!
x^(2(4)) =x^8 = (x^4)^2
3 - -3
54sqrt3. (divide the hexagon into 6 congruent equilateral triangles.

13. 1/6 in percent?
III
13
Diameter(Pi)
16.6666%

14. What is the order of operations?
130pi
PEMDAS (Parentheses Exponents Multiplication/Division Addition/Subtraction)
10! / (10-3)! = 720
An isosceles right triangle.

15. Simplify 4sqrt21 X 5sqrt2 / 10sqrt7
5
2sqrt6
A tangent is a line that only touches one point on the circumference of a circle.
No - only like radicals can be added.

16. What is the graph of f(x) shifted downward c units or spaces?
F(x) - c
A subset.
10
1 & 37/132

17. x^2 = 9. What is the value of x?
3 - -3
16^8 - 64^5 = (4^3)^5 = 4^15 - 16^8=(4^2)^8 = 4^16
C = (pi)d
87.5%

18. 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?
Pi is the ratio of a circle'S circumference to its diameter.
The third side is greater than the difference and less than the sum.
F(x + c)
52

19. What is the intersection of A and B?
2^9 / 2 = 256
An arc is a portion of a circumference of a circle.
The set of elements found in both A and B.
The union of A and B.

20. 5/8 in percent?
The sum of digits is divisible by 9.
The curve opens downward and the vertex is the maximum point on the graph.
A reflection about the axis.
62.5%

21. What is the 'Solution' for a system of linear equations?
1.7
(b + c)
1
The point of intersection of the systems.

22. 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)!
(amount of decrease/original price) x 100%
When we need to avoid having a zero in the denominator or avoid taking the square root of a number.
Two angles whose sum is 180.

23. A number is divisible by 9 if...
$11 -448
1
The sum of digits is divisible by 9.
20.5

24. What is an exterior angle?
Infinite.
A tangent is a line that only touches one point on the circumference of a circle.
(a - b)^2
An angle which is supplementary to an interior angle.

25. Circumference of a circle?
F(x) + c
F(x + c)
Diameter(Pi)
Circumference = Diameter(pi). Use pythagorean theorem to find the diagonal of the square (the diameter).

26. What is a finite set?
A set with a number of elements which can be counted.
Use Pythagorean theorem twice. (Once across the surface and then a is the diagonal of surface and b is an edge).
441000 = 1 10 10 10 21 * 21
Angle/360 x (pi)r^2

27. Which quandrant is the lower right hand?
IV
Its divisible by 2 and by 3.
1/2 times 7/3
All real numbers which can'T be expressed as a ratio of two integers - positive and negative (pi - -sqrt3)

28. Formula to find a circle'S circumference from its diameter?
When we need to avoid having a zero in the denominator or avoid taking the square root of a number.
(amount of decrease/original price) x 100%
C = (pi)d
A grouping of the members within a set based on a shared characteristic.

29. What is the name for a grouping of the members within a set based on a shared characteristic?
1
The two xes after factoring.
A subset.
C = 2(pi)r

30. A company places a 6-symbol code on each product. The code consists of the letter T - followed by 3 numerical digits - and then 2 consonants (Y is a conson). How many codes are possible?
(n-2) x 180
441000 = 1 10 10 10 21 * 21
23 - 29
A reflection about the origin.

31. What is the 'Range' of a series of numbers?
The greatest value minus the smallest.
4725
90pi
F(x-c)

32. The ratio of the areas of two similar polygons is ...
90 degrees
... the square of the ratios of the corresponding sides.
A 30-60-90 triangle.
20.5

33. Can the input value of a function have more than one output value (i.e. x: y - y1)?
180
A 30-60-90 triangle.
10! / (10-3)! = 720
No - the input value has exactly one output.

34. (6sqrt3) x (2sqrt5) =
3
(6 x 2)(sqrt3 x sqrt5) = 12sqrt15
An angle which is supplementary to an interior angle.
Yes - like radicals can be added/subtracted.

35. Write 10 -843 X 10^7 in scientific notation
1.0843 X 10^11
Infinite.
62.5%
The second graph is less steep.

36. Find the surface area of a cylinder with radius 3 and height 12.
The curve opens downward and the vertex is the maximum point on the graph.
1/(x^y)
(a - b)(a + b)
90pi

37. What is it called when a point is reflected to the quadrant opposite it (i.e. I to III or II to IV)?
13
A reflection about the origin.
The second graph is less steep.
3/2 - 5/3

38. What is the surface area of a cylinder with radius 5 and height 8?
130pi
II
Two angles whose sum is 180.
9 : 25

39. x^(-y)=
$11 -448
18
(p + q)/5
1/(x^y)

40. How to determine percent increase?
13
1/(x^y)
441000 = 1 10 10 10 21 * 21
(amount of increase/original price) x 100%

41. To convert a decimal to a percent...
...multiply by 100.
62.5%
288 (8 9 4)
Part = Percent X Whole

42. Evaluate 3& 2/7 / 1/3
9 & 6/7
Move the decimal point to the right x places
A 30-60-90 triangle.
Angle/360 x 2(pi)r

43. What is the common monomial factor in the expression 4(c^3)d - (c^2)(d^2) + 2cd?
Cd
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.
54sqrt3. (divide the hexagon into 6 congruent equilateral triangles.

44. Formula for the area of a circle?
28. n = 8 - k = 2. n! / k!(n-k)!
(amount of increase/original price) x 100%
A = pi(r^2)
1

45. To convert a percent to a fraction....
13
27^(-4)
53 - 59
Divide by 100.

46. In similar hexagons - the ratio of the areas is 16:25. What is the ratio of their corresponding sides?
4:5
No - only like radicals can be added.
83.333%
1

47. Evaluate and write as a mixed number: 2/7 - 3/21 + 2 & 4/14
130pi
11 - 13 - 17 - 19
2 & 3/7
(a + b)^2

48. Which is greater? 27^(-4) or 9^(-8)
1
The set of input values for a function.
x(x - y + 1)
27^(-4)

49. Can the output value of a function have more than one input value?
The objects within a set.
The set of input values for a function.
1.0843 X 10^11
Yes. [i.e. f(x) = x^2 - 1

50. (-1)^2 =
413.03 / 10^4 (move the decimal point 4 places to the left)
x(x - y + 1)
Ax^2 + bx + c where a -b and c are constants and a /=0
1