All GMAT Math Resources
Example Questions
Example Question #1571 : Problem Solving Questions
Examine the above diagram, which shows a Venn diagram representing the sets of real numbers.
and are both numbers in Region I; also, . In how many of the five regions could the number possibly fall?
Three
Five
Two
Four
One
Two
The numbers in Region I are exactly the natural numbers . All natural numbers are integers, and the integers are closed under subtraction, so cannot fall in Region IV or Region V. Also, since it is given in the problem that , it follows that , so the difference cannot be in Region II (the only whole number that is not a natural number is ).
It is possible for to be in Region I. Example:
It is possible for to be in Region III (the integers that are not whole numbers, or the negative integers). Example:
can fall in either of two different regions.
Example Question #16 : Sets
Examine the above diagram, which shows a Venn diagram representing the sets of real numbers.
and are both numbers in Region I; also, . In how many of the five regions could the number possibly fall?
Three
Five
Two
Four
One
Two
As natural numbers, and are also rational numbers; since the set of rational numbers is closed under division, and neither nor is equal to zero (zero not being a natural number), is rational and cannot fall in Region V. Regions III (negative integers) and II (zero only) can be eliminated, since both and are positive. This leaves Regions I and IV.
Examples can be produced that would place in Region I:
Examples can be produced that would place in Region IV (the rational numbers that are not integers):
can fall in either of two different regions.
Example Question #21 : Understanding Arithmetic Sets
Examine the above diagram, which shows a Venn diagram representing the sets of real numbers.
and are both numbers in Region V, and they may or may not be equal. In how many of the five regions could the number possibly fall?
Five
Two
Four
Three
One
Four
The numbers in Region V are the irrational numbers, such as and .
Since neither number can be the rational number zero, the product of the two cannot be zero, eliminating the possibility that . Region II comprises only this number—only 0 is a whole number but not a natural number—so Region II can be eliminated.
Examples can be produced that would place in any of the other four regions:
Case 1:
,
placing in Region I.
Case 2:
placing in Region III (the negative integers).
Case 3:
placing in Region IV (the non-integer rational numbers).
Case 4:
placing in Region V.
Therefore, can fall in any of four different regions.
Example Question #21 : Understanding Arithmetic Sets
Given five sets , you are given that:
All of the following must be true if except:
None of the other choices gives a correct answer.
The subset relation is transitive, so and together imply that .
Since all three of are subsets of , then any element of any of those four sets is an element of . Contrapositively, any nonelement of cannot be an element of any of .
However, it is possible for a nonelement of to be an element of if . A simple example:
and .
, , and .
Example Question #21 : Arithmetic
Given five sets , you are given that:
All of the following must be true if except:
None of the other choices gives a correct answer.
None of the other choices gives a correct answer.
The subset relation is transitive, so:
and together imply that ;
and together imply that ; and,
and together imply that .
Since all four of are subsets of , then any element of any of those four sets is an element of . Contrapositively, any nonelement of cannot be an element of any of .
Example Question #22 : Understanding Arithmetic Sets
Define two sets as follows:
. Which is a possible value of ?
comprises the set of all odd integers except 1; comprises the set of all integers of the form , a natural number. Therefore, any number that is not in the union of these two sets must be in neither one.
, so is even or 1 (although 1 is not a choice). We can eliminate odd choices 147, 149, and 151 immediately.
, so we determine which number cannot be expressed as , a natural number.
148 is elminated, since it is two less than a multiple of 3. 150 is the correct choice.
Example Question #22 : Arithmetic
Define three sets as follows:
How many elements does the set have?
Infinitely many
The intersection of and is the set of all elements in that are also in - namely, . The union of this set and is the set of all elements in one or the other set, or .
The set has seven elements.
Example Question #26 : Sets
Define three sets as follows:
How many elements does the set have?
None of the other responses gives a correct answer.
Infinitely many.
comprises the set of elements common to all three sets. Only 5 fulfills that condition, so the correct choice is 1.
Example Question #23 : Arithmetic
Define three sets as follows:
How many elements does the set have?
Infinitely many
comprises the set of elements common to all three sets. However, since is the set of all even integers and comprises the set of all odd integers, no element can be common to all three sets. The correct response is 0.
Example Question #21 : Understanding Arithmetic Sets
The Fibonacci sequence is the sequence defined as follows:
For all integers , .
Which of the following expressions is equal to ?
Each term after the second is the sum of the preceding two, ao we can relate the 100th term to the 96th and 97th terms as follows: