All PSAT Math Resources
Example Questions
Example Question #1 :How To Subtract Even Numbers
Ifis an odd integer andis an even integer, which of the following must true of?
The result will be odd.
The result will be even.
We cannot draw any conclusions from the given information.
The result will be odd.
An even number subtracted from an odd number will always produce an odd result.
None of the other answer choices are correct.
Example Question #21 :Even / Odd Numbers
Ifxrepresents an even integer, which of the following expressions represents an odd integer?
3x+ 1
5x+ 4
x+ 2
2x– 2
3x– 2
3x+ 1
Pick any even integer (2, 4, 6, etc.) to representx.唯一的价值是奇怪的是3x+ 1. Any number multiplied by an even integer will be even. When an even number is added and subtracted to that product, the result will be even as well. 3x+ 1是唯一的选择,增加了一个奇数the product.
Example Question #1 :How To Divide Even Numbers
Ifmandnare both even integers, which of the following must be true?
l.m2/n2is even
ll.m2/n2is odd
lll.m2+n2is divisible by four
I & III only
II only
none
III only
I only
III only
While I & II can be true, examples can be found that show they are not always true (for example, 22/22is odd and 42/22is even).
III is always true – a square even number is always divisible by four, and the distributive property tell us that adding two numbers with a common factor gives a sum that also has that factor.
Example Question #2 :How To Divide Even Numbers
LetSbe a set that consists entirely of even integers, and letTbe the set that consists of each of the elements inSincreased by two. Which of the following must be even?
I. the mean ofT
II. the median ofT
III. the range ofT
I and II only
II and III only
II only
I only
III only
III only
Sconsists of all even integers. If we were to increase each of these even numbers by 2, then we would get another set of even numbers, because adding 2 to an even number yields an even number. In other words,Talso consists entirely of even numbers.
In order to find the mean ofT, we would need to add up all of the elements inTand then divide by however many numbers are inT.If we were to add up all of the elements ofT, we would get an even number, because adding even numbers always gives another even number. However, even though the sum of the elements inTmust be even, if the number of elements inTwas an even number, it's possible that dividing the sum by the number of elements ofTwould be an odd number.
For example, let's assumeTconsists of the numbers 2, 4, 6, and 8. If we were to add up all of the elements ofT, we would get 20. We would then divide this by the number of elements inT, which in this case is 4. The mean ofTwould thus be 20/4 = 5, which is an odd number. Therefore, the mean ofTdoesn't have to be an even number.
Next, let's analyze the median ofT.Again, let's pretend thatTconsists of an even number of integers. In this case, we would need to find the average of the middle two numbers, which means we would add the two numbers, which gives us an even number, and then we would divide by two, which is another even number. The average of two even numbers doesn't have to be an even number, because dividing an even number by an even number can produce an odd number.
For example, let's pretendTconsists of the numbers 2, 4, 6, and 8. The median ofTwould thus be the average of 4 and 6. The average of 4 and 6 is (4+6)/2 = 5, which is an odd number. Therefore, the median ofTdoesn't have to be an even number.
Finally, let's examine the range ofT.The range is the difference between the smallest and the largest numbers inT, which both must be even. If we subtract an even number from another even number, we will always get an even number. Thus, the range ofTmust be an even number.
Of choices I, II, and III, only III must be true.
The answer is III only.
Example Question #22 :Even / Odd Numbers
If x is an even integer and y is an odd integer. Which of these expressions represents an odd integer?
I. xy
II. x-y
III. 3x+2y
I and III only
II only
I, II, and III only
II and III only
I and II only
II only
I)xy is Even*Odd is Even. II) x-y is Even+/-Odd is Odd. III) 3x is Odd*Even =Even, 2y is Even*Odd=Even, Even + Even = Even. Therefore only II is Odd.
Example Question #23 :Even / Odd Numbers
If x is an even number, y is an odd number, and z is an even number, which of the following will always give an even number?
I. xyz
II. 2x+3y
III. z2– y
I, II and III
II and III only
II only
I only
I and II only
I only
I. xyz = even * odd * even = even
II. 2x + 3y = even*even + odd*odd = even + odd = odd
III. z2– y = even * even – odd = even – odd = odd
Therefore only I will give an even number.
Example Question #24 :Even / Odd Numbers
Ifxandyare integers and at least one of them is even, which of the following MUST be true?
xyis odd
x+yis even
Nothing can be determined based on the given information
x+yis odd
xyis even
xyis even
Since we are only told that "at least" one of the numbers is even, we could have one even and one odd integer OR we could have two even integers.
Even plus odd is odd, but even plus even is even, sox+ycould be either even or odd.
Even times odd is even, and even times even is even, soxymust be even.
Example Question #25 :Even / Odd Numbers
Letaandbbe positive integers such thatab2is an even number. Which of the following must be true?
I.a2is even
II.a2bis even
III.abis even
I only
II and III only
II only
I, II, and III
I and II only
II and III only
In order to solve this problem, it will help us to find all of the possible scenarios ofa,b,a2, andb2.We need to make use of the following rules:
1. The product of two even numbers is an even number.
2. The product of two odd numbers is an odd number.
3. The product of an even and an odd number is an even number.
The information that we are given is thatab2is an even number. Let's think ofab2as the product of two integers:aandb2.
In order for the product ofaandb2to be even, at least one of them must be even, according to the rules that we discussed above. Thus, the following scenarios are possible:
Scenario 1:ais even andb2is even
Scenario 2:ais even andb2is odd
Scenario 3:ais odd andb2is even
Next, let's consider what possible values are possible forb.Ifb2is even, then this meansbmust be even, because the product of two even numbers is even. Ifbwere odd, then we would have the product of two odd numbers, which would mean thatb2would be odd. Thus, ifb2is even, thenbmust be even, and ifb2is odd, thenbmust be odd. Let's add this information to the possible scenarios:
Scenario 1:ais even,b2is even, andbis even
Scenario 2:ais even,b2is odd, andbis odd
Scenario 3:ais odd,b2is even, andbis even
Lastly, let's see what is possible fora2.Ifais even, thena2must be even, and ifais odd, thena2must also be odd. We can add this information to the three possible scenarios:
Scenario 1:ais even,b2is even, andbis even, anda2is even
Scenario 2:ais even,b2is odd, andbis odd, anda2is even
Scenario 3:ais odd,b2is even, andbis even, anda2is odd
Now, we can use this information to examine choices I, II, and III.
Choice I asks us to determine ifa2must be even. If we look at the third scenario, in whichais odd, we see thata2would also have to be odd. Thus it is possible fora2to be odd.
Next, we can analyzea2b.In the first scenario, we see thata2is even andbis even. This means thata2bwould be even. In the second scenario, we see thata2is even, andbis odd, which would still mean thata2bis even. And in the third scenario,a2is odd andbis even, which also means thata2bwould be even. In short,a2bis even in each of the possible scenarios, so it must always be even. Thus, choice II must be true.
We can now look atab.In scenario 1,ais even andbis even, which means thatabwould also be even. In scenario2,ais even andbis odd, which means thatabis even again. And in scenario 3,ais odd andbis even, which again means thatabis even. Therefore,abmust be even, and choice III must be true.
The answer is II and III only.
Example Question #26 :Even / Odd Numbers
Letequal the product of two numbers. If, then the two numbers COULD be which of the following?
20 and 4
32 and 2
2 and 8
0 and 16
8 and 8
2 and 8
The word "product" refers to the answer of a multiplication problem. Since 2 times 8 equals 16, it is a valid pair of numbers.
Example Question #27 :Even / Odd Numbers
Ifandis an odd integer, which of the following couldbe divisible by?
Ifis an odd integer then we can plug 1 intoand solve foryielding 13. 13 is prime, meaning it is only divisible by 1 and itself.
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