Integers - ACT Math
Card 0 of 1710
is even
is even
Therefore, which of the following must be true about
?
is even
is even
Therefore, which of the following must be true about ?
Recall that when you multiply by an even number, you get an even product.
Therefore, we know the following from the first statement:
is even or
is even or both
and
are even.
For the second, we know this:
Since
is even, therefore,
can be either even or odd. (Regardless of what it is, we can get an even value for
.)
Based on all this data, we can tell nothing necessarily about
. If
is even, then
is even, even if
is odd. However, if
is odd while
is even, then
will be even.
Recall that when you multiply by an even number, you get an even product.
Therefore, we know the following from the first statement:
is even or
is even or both
and
are even.
For the second, we know this:
Since is even, therefore,
can be either even or odd. (Regardless of what it is, we can get an even value for
.)
Based on all this data, we can tell nothing necessarily about . If
is even, then
is even, even if
is odd. However, if
is odd while
is even, then
will be even.
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A student is taking a test consisting of six questions. It is a multiple choice test and each question has four answers labelled A, B, C, and D. How many ways can the student answer all six questions if he does not choose the same answer for any two consecutive questions?
A student is taking a test consisting of six questions. It is a multiple choice test and each question has four answers labelled A, B, C, and D. How many ways can the student answer all six questions if he does not choose the same answer for any two consecutive questions?
the student has four choices for the first question, but only three choices for each of the remaining questions since he does not choose answers with the same letter twice in a row. From the multiplicative counting principle, there are 4 × 3 × 3 × 3 × 3 x 3 = 972 ways Steve can answer the six questions.
the student has four choices for the first question, but only three choices for each of the remaining questions since he does not choose answers with the same letter twice in a row. From the multiplicative counting principle, there are 4 × 3 × 3 × 3 × 3 x 3 = 972 ways Steve can answer the six questions.
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A locker combination consists of three different numbers from the set of 30 different numbers on the face of the lock. Imagine that you have forgotten the combination. How many times do you have to try to find the right combination?
A locker combination consists of three different numbers from the set of 30 different numbers on the face of the lock. Imagine that you have forgotten the combination. How many times do you have to try to find the right combination?
It is said that the three numbers are different. So the number of lock combinations is 30_P_3 = 24 360.
It is said that the three numbers are different. So the number of lock combinations is 30_P_3 = 24 360.
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Which of the following expressions is odd for any integers
and
?
Which of the following expressions is odd for any integers and
?
The key here is for any integers
and
, that means that no matter what you set
and
equal to you will get an odd number. An odd number is not divisible by 2, also it is an even number plus and odd number. The only expression that satisfies this is
.
will always be even, so will
, but
is always odd so the combination gives us an odd number, always.
The key here is for any integers and
, that means that no matter what you set
and
equal to you will get an odd number. An odd number is not divisible by 2, also it is an even number plus and odd number. The only expression that satisfies this is
.
will always be even, so will
, but
is always odd so the combination gives us an odd number, always.
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The game of euchre uses the 9s, 10s, jacks, queens, kings, and aces from a standard deck of 52 cards. How many 5-card euchre hands have at least 2 black cards?
The game of euchre uses the 9s, 10s, jacks, queens, kings, and aces from a standard deck of 52 cards. How many 5-card euchre hands have at least 2 black cards?
The hand could have 2, 3, 4, or 5 black cards. There are 12 black cards and 12 red cards, so the numbers of combinations for the four cases are as follows.
2 black cards: C(12, 2) × C(12, 3) = 14 520
3 black cards: C(12, 3) × C(12, 2) = 14 520
4 black cards: C(12, 4) × C(12, 1) = 5940
5 black cards: C(12, 5) × C(12, 0) = 792
The total number of euchre hands that have at least two black cards is the total of these four cases, 35 772.
The hand could have 2, 3, 4, or 5 black cards. There are 12 black cards and 12 red cards, so the numbers of combinations for the four cases are as follows.
2 black cards: C(12, 2) × C(12, 3) = 14 520
3 black cards: C(12, 3) × C(12, 2) = 14 520
4 black cards: C(12, 4) × C(12, 1) = 5940
5 black cards: C(12, 5) × C(12, 0) = 792
The total number of euchre hands that have at least two black cards is the total of these four cases, 35 772.
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Evaluate: 
Evaluate:
For this problem, align and solve by adding the ones digit
, tens digit
, and hundreds digit
. This also means that you have to add
to the
in the thousands place to get
.

For this problem, align and solve by adding the ones digit , tens digit
, and hundreds digit
. This also means that you have to add
to the
in the thousands place to get
.
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Find the sum of 12 and 42.
Find the sum of 12 and 42.
Rewrite the question into a mathematical expression.

Add the ones digit.

Add the tens digit.

Combine the tens digit and the ones digit. The answer is
.
Rewrite the question into a mathematical expression.
Add the ones digit.
Add the tens digit.
Combine the tens digit and the ones digit. The answer is .
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Solve: 
Solve:
Add the ones digits:

Since there is no tens digit to carry over, proceed to add the tens digits:

The answer is
.
Add the ones digits:
Since there is no tens digit to carry over, proceed to add the tens digits:
The answer is .
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At a certain high school, everyone must take either Latin or Greek. There are
more students taking Latin than there are students taking Greek. If there are
students taking Greek, how many total students are there?
At a certain high school, everyone must take either Latin or Greek. There are more students taking Latin than there are students taking Greek. If there are
students taking Greek, how many total students are there?
If there are
students taking Greek, then there are
or
students taking Latin. However, the question asks how many total students there are in the school, so you must add these two values together to get:
or
total students.
If there are students taking Greek, then there are
or
students taking Latin. However, the question asks how many total students there are in the school, so you must add these two values together to get:
or
total students.
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Divide: 
Divide:
Rewrite
and use common factors to simplify.

Rewrite and use common factors to simplify.
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Find the sum of 13 and 19.
Find the sum of 13 and 19.
Rewrite the question in a mathematical expression.

Add the ones digit.

Since this number is larger than
, carry over the
in tens digit when adding the next term.
Add the tens digit with the carry over.

Combine the tens digit and the ones digit. The answer is
.
Rewrite the question in a mathematical expression.
Add the ones digit.
Since this number is larger than , carry over the
in tens digit when adding the next term.
Add the tens digit with the carry over.
Combine the tens digit and the ones digit. The answer is .
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In order to get an odd result from an addition, we must have one odd and one even number, thus you know from the first point about
that only one of the two values is odd. Now, to get an even result, you can have two evens or two odds. So, let's presume that
has two odd values, this means that
must be even. Thus, you have:

Now, if we presume that
has two even values, we must then know that
is odd. Thus, we have:

First of all, you can eliminate the two answers that say that a given value is positive or negative. This cannot be told from our data. Next, it cannot be the case that
is even. It will always be odd (hence, the correct answer is this). Finally, it cannot be that
is even always. In the second case above, you will have two even numbers added together, given you an even. Then, you will add in an odd, giving you an odd.
In order to get an odd result from an addition, we must have one odd and one even number, thus you know from the first point about that only one of the two values is odd. Now, to get an even result, you can have two evens or two odds. So, let's presume that
has two odd values, this means that
must be even. Thus, you have:
Now, if we presume that has two even values, we must then know that
is odd. Thus, we have:
First of all, you can eliminate the two answers that say that a given value is positive or negative. This cannot be told from our data. Next, it cannot be the case that is even. It will always be odd (hence, the correct answer is this). Finally, it cannot be that
is even always. In the second case above, you will have two even numbers added together, given you an even. Then, you will add in an odd, giving you an odd.
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Solve: 
Solve:
This problem can be solved using common factors.
Rewrite
using factors.

This problem can be solved using common factors.
Rewrite using factors.
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Divide: 
Divide:
Rewrite
by using factors. Simplify until the answer cannot be reduced any further.

Rewrite by using factors. Simplify until the answer cannot be reduced any further.
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Divide: 
Divide:
Rewrite
by using common factors. Reduce to the simplest form.

Rewrite by using common factors. Reduce to the simplest form.
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Choose the answer which best solves the equation below:

Choose the answer which best solves the equation below:
There are two ways to solve this problem. First you can do so algebraically by dividing both sides by 13:


But, there is another way, which if you understand odd numbers, is even faster. Of all the answers above, only one is odd. You know, given the equation, that
must be odd--any odd number multiplied by an odd number will yeild an odd number. If you multiply an odd number by an even number, you will get an even number.
There are two ways to solve this problem. First you can do so algebraically by dividing both sides by 13:
But, there is another way, which if you understand odd numbers, is even faster. Of all the answers above, only one is odd. You know, given the equation, that must be odd--any odd number multiplied by an odd number will yeild an odd number. If you multiply an odd number by an even number, you will get an even number.
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Solve for
in the following equation:

Solve for in the following equation:
There are two ways to approach this problem:
1. Use the rule that states that any two odd numbers multiplied together will yield another odd number.
Using this rule, only one answer is an odd number (29) which will yield another odd number (493) when multiplied by the given odd number (17).
2. Solve algebraically:


There are two ways to approach this problem:
1. Use the rule that states that any two odd numbers multiplied together will yield another odd number.
Using this rule, only one answer is an odd number (29) which will yield another odd number (493) when multiplied by the given odd number (17).
2. Solve algebraically:
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Solve for
in the follwing equation:

Solve for in the follwing equation:
There are two ways to approach this problem:
1. Use the rule that states that any two odd numbers multiplied together will yield another odd number.
Using this rule, only one answer is an odd number (85) which will yield another odd number (7,735) when multiplied by the given odd number (91).
2. Solve algebraically:


There are two ways to approach this problem:
1. Use the rule that states that any two odd numbers multiplied together will yield another odd number.
Using this rule, only one answer is an odd number (85) which will yield another odd number (7,735) when multiplied by the given odd number (91).
2. Solve algebraically:
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Which of the following integers has an even integer value for all positive integers
and
?
Which of the following integers has an even integer value for all positive integers and
?
There are certain patterns that can be used to predict whether the product or sum of numbers will be odd or even. The sum of two odd numbers is always even, as is the sum of two even numbers. The sum of an odd number and an even number is always odd. In multiplication the product of two odd numbers is always odd. While the product of even numbers, as well as the product of odd numbers multiplied by even numbers is always even. So for this problem we need to find scenarios where the only possibile answers are even.
can only result in even numbers no matter what positive integers are used for
and
, because
must can only result in even products; the same can be said for
. The rules provide that the sum of two even numbers is even, so
is the answer.
There are certain patterns that can be used to predict whether the product or sum of numbers will be odd or even. The sum of two odd numbers is always even, as is the sum of two even numbers. The sum of an odd number and an even number is always odd. In multiplication the product of two odd numbers is always odd. While the product of even numbers, as well as the product of odd numbers multiplied by even numbers is always even. So for this problem we need to find scenarios where the only possibile answers are even. can only result in even numbers no matter what positive integers are used for
and
, because
must can only result in even products; the same can be said for
. The rules provide that the sum of two even numbers is even, so
is the answer.
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You work as a health inspector and must visit each of the 15 restaurants in town once each week. In how many different orders can you make these inspections?
You work as a health inspector and must visit each of the 15 restaurants in town once each week. In how many different orders can you make these inspections?
15_P_15 = 15!
= 1.307 674 368 × 1012
15_P_15 = 15!
= 1.307 674 368 × 1012
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