Systems of Equations

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SAT Math › Systems of Equations

Questions 1 - 10
1

The sum of four consecutive even integers is , but their product is . What is the least of those integers?

Explanation

Any time the product of consecutive numbers is , must be a one of those consecutive numbers, because if it is not, the product will be non-zero. This leaves us with four possibilities, depending on where is placed in the sequence.

As we can see, , , and are our numbers in question, meaning is our answer as the lowest number.

Note that it is possible to use algebra and set up a system of equations, but it's more time-consuming, which could hinder more than help in a standardized test setting.

2

If 7_x_ + y = 25 and 6_x_ + y = 23, what is the value of x?

2

6

7

11

20

Explanation

You can subtract the second equation from the first equation to eliminate y:

7_x_ + y = 25 – 6_x_ + y = 23: 7_x_ – 6_x_ = x; yy = 0; 25 – 23 = 2

x = 2

You could also solve one equation for y and substitute that value in for y in the other equation:

6_x_ + y = 23 → y = 23 – 6_x_.

7_x_ + y = 25 → 7_x_ + (23 – 6_x_) = 25 → x + 23 = 25 → x = 2

3

The sum of four consecutive even integers is , but their product is . What is the least of those integers?

Explanation

Any time the product of consecutive numbers is , must be a one of those consecutive numbers, because if it is not, the product will be non-zero. This leaves us with four possibilities, depending on where is placed in the sequence.

As we can see, , , and are our numbers in question, meaning is our answer as the lowest number.

Note that it is possible to use algebra and set up a system of equations, but it's more time-consuming, which could hinder more than help in a standardized test setting.

4

If 7_x_ + y = 25 and 6_x_ + y = 23, what is the value of x?

2

6

7

11

20

Explanation

You can subtract the second equation from the first equation to eliminate y:

7_x_ + y = 25 – 6_x_ + y = 23: 7_x_ – 6_x_ = x; yy = 0; 25 – 23 = 2

x = 2

You could also solve one equation for y and substitute that value in for y in the other equation:

6_x_ + y = 23 → y = 23 – 6_x_.

7_x_ + y = 25 → 7_x_ + (23 – 6_x_) = 25 → x + 23 = 25 → x = 2

5

How many solutions are there to the following system of equations?

There are an infinite number of solutions.

There is 1 single solution.

There are 2 solutions.

There are 3 solutions.

There are no solutions.

Explanation

If we use elimination to solve this system of equations, we can add the two equations together. This results in 0=0.

When elimination results in 0=0, that means that the two equations represent the same line. Therefore, there are an infinite number of solutions.

6

How many solutions are there to the following system of equations?

There are an infinite number of solutions.

There is 1 single solution.

There are 2 solutions.

There are 3 solutions.

There are no solutions.

Explanation

If we use elimination to solve this system of equations, we can add the two equations together. This results in 0=0.

When elimination results in 0=0, that means that the two equations represent the same line. Therefore, there are an infinite number of solutions.

7

At what point will the lines \dpi{100} \small 4x+2=y and \dpi{100} \small 3x+3=y intersect?

(1, 6)

(1, –6)

(6, 1)

(–1, 6)

(6, –1)

Explanation

In order to find this point, we must find the solution to the system of equations. we will use substitution, setting the two expressions for y equal to one another.

\dpi{100} \small 4x+2=3x+3 \rightarrow x=1

Then we plug this value back into either expression for y, giving us \dpi{100} \small y=4\times 1+2=6

So the point is (1, 6).

8

At what point will the lines \dpi{100} \small 4x+2=y and \dpi{100} \small 3x+3=y intersect?

(1, 6)

(1, –6)

(6, 1)

(–1, 6)

(6, –1)

Explanation

In order to find this point, we must find the solution to the system of equations. we will use substitution, setting the two expressions for y equal to one another.

\dpi{100} \small 4x+2=3x+3 \rightarrow x=1

Then we plug this value back into either expression for y, giving us \dpi{100} \small y=4\times 1+2=6

So the point is (1, 6).

9

What is the value of in the following system of equations? Round your answer to the hundredths place.

Explanation

You can solve this problem in a number of ways, but one way to solve it is by using substitution. You can begin to do that by solving for in the first equation:

Now, you can substitute in that value of into the second equation and solve for :

Let's consider this equation as adding a negative 3 rather than subtracting a 3 to make distributing easier:

Distribute the negative 3:

We can now combine like variables and solve for :

10

What is the value of in the following system of equations? Round your answer to the hundredths place.

Explanation

You can solve this problem in a number of ways, but one way to solve it is by using substitution. You can begin to do that by solving for in the first equation:

Now, you can substitute in that value of into the second equation and solve for :

Let's consider this equation as adding a negative 3 rather than subtracting a 3 to make distributing easier:

Distribute the negative 3:

We can now combine like variables and solve for :

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