PSAT Math : PSAT Mathematics

Study concepts, example questions & explanations for PSAT Math

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Example Questions

Example Question #3 : Creating Equations With Whole Numbers

What is the solution of  for the two systems?

Possible Answers:

Correct answer:

Explanation:

We first multiply the second equation by 4.

So our resulting equation is:

Then we subtract the first equation from the second new equation.

Left Hand Side:

Right Hand Side:

Resulting Equation:

 

We divide both sides by -15

Left Hand Side:

Right Hand Side:

Our result is:

 

Example Question #12 : How To Find The Solution For A System Of Equations

Find the solutions for the following set of equations:

 

Possible Answers:

Correct answer:

Explanation:

If we multiply both sides of our bottom equation by , we get . We can now add our two equations, and eliminate , leaving only one variable. When we add the equations, we get . Therefore, . Finally, we go back to either of our equations, and plug in  so we can solve for .

 

Example Question #11 : How To Find The Solution For A System Of Equations

Give the solution to the system of equations below.

 

Possible Answers:

No solution

Correct answer:

Explanation:

Solve the second equation for , allowing us to solve using the substitution method.

Substitute for   in the first equation, and solve for .

Now, substitute for  in either equation; we will choose the second. This allows us to solve for .

Now we can write the solution in the notation , or .

Example Question #1 : How To Find The Solution To An Inequality With Subtraction

|12x + 3y| < 15

What is the range of values for y, expressed in terms of x?

Possible Answers:

–5 – 4x < y < 5 – 4x

y > 15 – 12x

5 – 4x < y < 5 + 4x

5 + 4x < y < 5 – 4x

y < 5 – 4x

Correct answer:

–5 – 4x < y < 5 – 4x

Explanation:

Recall that with absolute values and "less than" inequalities, we have to hold the following:

12x + 3y < 15

AND

12x + 3y > –15

Otherwise written, this is:

–15 < 12x + 3y < 15

In this form, we can solve for y. First, we have to subtract x from all 3 parts of the inequality:

–15 – 12x < 3y < 15 – 12x

Now, we have to divide each element by 3:

(–15 – 12x)/3 < y < (15 – 12x)/3

This simplifies to:

–5 – 4x < y < 5 – 4x

Example Question #1 : Inequalities

|4x + 14| > 30

What is a possible valid value of x?

Possible Answers:

1

7

4

–3

–11

Correct answer:

7

Explanation:

This inequality could be rewritten as:

4x + 14 > 30  OR 4x + 14 < –30

Solve each for x:

4x + 14 > 30; 4x > 16; x > 4

4x + 14 < –30; 4x < –44; x < –11

Therefore, anything between –11 and 4 (inclusive) will not work. Hence, the answer is 7.

Example Question #2 : Inequalities

Given the inequality,  |2x – 2|  >  20,

what is a possible value for x?

Possible Answers:

11

10

0

–8

–10

Correct answer:

–10

Explanation:

For this problem, we must take into account the absolute value.

First, we solve for 2x – 2 > 20.  But we must also solve for 2x – 2 < –20 (please notice that we negate 20 and we also flip the inequality sign).  

First step:

2x – 2 > 20

2x > 22

x > 11

Second step:

2x – 2 < –20

2x < –18

x < –9

Therefore, x > 11 and x < –9.

A possible value for x would be –10 since that is less than –9.  

Note: the value 11 would not be a possible value for x because the inequality sign given does not include an equal sign.

Example Question #3 : Inequalities

Solve for x.

-2x+5\leq 10

Possible Answers:

x\leq \frac{5}{2}

x\leq 5

x\geq \frac{5}{2}

None\ of\ the\ above

x\geq -\frac{5}{2}

Correct answer:

x\geq -\frac{5}{2}

Explanation:

Move +5 using subtraction rule which will give you-2x\leq 5

Divide both sides by 2 (using division rule) and you will get -x\leq \frac{5}{2} which is the same as x\geq \frac{5}{2}

Example Question #4 : Inequalities

If \frac{a}{5}+5> 6, which of the following MUST be true?

 

I. a> 2

II. a> 10

III. a< 6

Possible Answers:

I only

I and II only

III only

II only

I, II, and III

Correct answer:

I only

Explanation:

Subtract 5 from both sides of the inequality:

\frac{a}{5}> 1

Multiply both sides by 5:

a> 5

Therefore only I must be true.

Example Question #5 : Inequalities

Which of the following is equivalent to ?

Possible Answers:

Correct answer:

Explanation:

Solve for both x – 3 < 2 and –(x – 3) < 2.

x – 3 < 2 and –x + 3 < 2

x < 2 + 3 and –x < 2 – 3

x < 5 and –x < –1

x < 5 and x > 1

The results are x < 5 and x > 1.

Combine the two inequalities to get 1 < x < 5

Example Question #6 : Inequalities

Which of the following is a possible set of solutions to ?

Possible Answers:

Correct answer:

Explanation:

Manipulate the inequality until  is on a side by itself:

For this equation,  must be less than 6. Find the answer choice with values all less than 6. In this case, it will be -1, 4, and 5.

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