SAT Math : Equations / Inequalities

Study concepts, example questions & explanations for SAT Math

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Example Questions

Example Question #3 : Inequalities

What is the solution set of the inequality \dpi{100} \small 3x+8<35\(\displaystyle \dpi{100} \small 3x+8< 35\) ?

Possible Answers:

\dpi{100} \small x<27\(\displaystyle \dpi{100} \small x< 27\)

\dpi{100} \small x>9\(\displaystyle \dpi{100} \small x>9\)

\dpi{100} \small x>27\(\displaystyle \dpi{100} \small x>27\)

\dpi{100} \small x<35\(\displaystyle \dpi{100} \small x< 35\)

\dpi{100} \small x<9\(\displaystyle \dpi{100} \small x< 9\)

Correct answer:

\dpi{100} \small x<9\(\displaystyle \dpi{100} \small x< 9\)

Explanation:

We simplify this inequality similarly to how we would simplify an equation

\dpi{100} \small 3x+8-8<35-8\(\displaystyle \dpi{100} \small 3x+8-8< 35-8\)

\dpi{100} \small \frac{3x}{3}<\frac{27}{3}\(\displaystyle \dpi{100} \small \frac{3x}{3}< \frac{27}{3}\)

Thus \dpi{100} \small x<9\(\displaystyle \dpi{100} \small x< 9\)

Example Question #4 : Inequalities

What is a solution set of the inequality \(\displaystyle 2x+12>42\)?

Possible Answers:

\(\displaystyle x>4\)

\(\displaystyle x< 9\)

\(\displaystyle x< 15\)

\(\displaystyle x>\frac{3}{2}\)

\(\displaystyle x>15\)

Correct answer:

\(\displaystyle x>15\)

Explanation:

In order to find the solution set, we solve \(\displaystyle 2x+12>42\) as we would an equation:

\(\displaystyle 2x+12>42\)

\(\displaystyle 2x>30\)

\(\displaystyle x>15\)

Therefore, the solution set is any value of \(\displaystyle x>15\).

Example Question #11 : Solving Inequalities

Which of the following could be a value of \(\displaystyle x\), given the following inequality?

\(\displaystyle 8-7x\leq11x+4\)

Possible Answers:

\(\displaystyle -\frac{1}{3}\)

\(\displaystyle -\frac{2}{3}\)

\(\displaystyle \frac{4}{9}\)

\(\displaystyle -\frac{2}{9}\)

\(\displaystyle \frac{1}{9}\)

Correct answer:

\(\displaystyle \frac{4}{9}\)

Explanation:

The inequality that is presented in the problem is:

\(\displaystyle 8-7x\leq11x+4\)

Start by moving your variables to one side of the inequality and all other numbers to the other side:

\(\displaystyle -7x-11x\leq4-8\)

\(\displaystyle -18x\leq-4\)

Divide both sides of the equation by \(\displaystyle -18\). Remember to flip the direction of the inequality's sign since you are dividing by a negative number!

\(\displaystyle x\geq\frac{-4}{-18}\)

Reduce:

\(\displaystyle x\geq\frac{2}{9}\)

The only answer choice with a value greater than \(\displaystyle \frac{2}{9}\) is \(\displaystyle \frac{4}{9}\).

Example Question #62 : New Sat Math Calculator

If \(\displaystyle 2\leq n \leq12\) and \(\displaystyle 9\leq p \leq10\), which of the following gives the set of possible values of \(\displaystyle \frac{n}{p}\)?

Possible Answers:

\(\displaystyle \frac{2}{9} \leq \frac{n}{p} \leq \frac{6}{5}\)

\(\displaystyle \frac{1}{5} \leq \frac{n}{p} \leq \frac{6}{5}\)

\(\displaystyle \frac{1}{5}\leq \frac{n}{p} \leq \frac{4}{3}\)

\(\displaystyle \frac{2}{9} \leq \frac{n}{p} \leq \frac{5}{6}\)

\(\displaystyle 0 \leq \frac{n}{p} \leq \frac{1}{5}\)

Correct answer:

\(\displaystyle \frac{1}{5}\leq \frac{n}{p} \leq \frac{4}{3}\)

Explanation:

To get the lowest value, you need the lowest numerator and the highest denominator.  That would be \(\displaystyle \frac{2}{10}\) or reduced to be \(\displaystyle \frac{1}{5}\).  For the highest value, you need the highest numerator and the lowest denominator.  That would be \(\displaystyle \frac{12}{9}\) or \(\displaystyle \frac{4}{3}\).

Example Question #161 : Algebra

Give the solution set of this inequality:

\(\displaystyle |- 5 x + 32| \le 38\)

Possible Answers:

\(\displaystyle [ -14 , 1.2]\)

\(\displaystyle [-1.2, 14 ]\)

The inequality has no solution.

\(\displaystyle ( -\infty, -14] \cup [1.2, \infty)\)

\(\displaystyle ( -\infty, -1.2] \cup [14 , \infty)\)

Correct answer:

\(\displaystyle [-1.2, 14 ]\)

Explanation:

The inequality \(\displaystyle |- 5 x + 32| \le 38\) can be rewritten as the three-part inequality

\(\displaystyle -38 \le - 5 x + 32 \le 38\)

Isolate the \(\displaystyle x\) in the middle expression by performing the same operations in all three expressions. Subtract 32 from each expression:

\(\displaystyle -38 - 32 \le - 5 x + 32 - 32 \le 38 - 32\)

\(\displaystyle -70 \le - 5 x \le 6\)

Divide each expression by \(\displaystyle -5\), switching the direction of the inequality symbols:

\(\displaystyle -70\div (-5) \ge - 5 x\div (-5) \ge 6 \div (-5)\)

\(\displaystyle 14 \ge x \ge -1.2\)

This can be rewritten in interval notation as \(\displaystyle [-1.2, 14 ]\).

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

Give the solution set of this inequality:

\(\displaystyle - 12 - | -4y + 52 | > 32\)

Possible Answers:

The inequality has no solution.

\(\displaystyle [-24,2 ]\)

\(\displaystyle (-\infty, -24 ]\cup [2, \infty)\)

\(\displaystyle [-2,24 ]\)

\(\displaystyle (-\infty, -2 ]\cup [24, \infty)\)

Correct answer:

The inequality has no solution.

Explanation:

In an absolute value inequality, the absolute value expression must be isolated first, as follows:

\(\displaystyle - 12 - | -4y + 52 | > 32\)

Adding 12 to both sides:

\(\displaystyle - 12 - | -4y + 52 | + 12 >32+ 12\)

\(\displaystyle - | -4y + 52 | >44\)

Multiplying both sides by \(\displaystyle -1\), and switching the inequality symbol due to multiplication by a negative number:

\(\displaystyle - | -4y + 52 | \cdot (-1 ) < 44 \cdot (-1 )\)

\(\displaystyle | -4y + 52 | < -44\)

We do not need to go further. An absolute value expression must always be greater than or equal to 0; it is impossible for the expression \(\displaystyle | -4y + 52 |\) to be less than any negative number. The inequality has no solution.

Example Question #161 : Equations / Inequalities

Find the sum of all of the integer values of x that satisfy the following inequality:

|4 – 2x| < 5

Possible Answers:

10

6

9

1

4

Correct answer:

10

Explanation:

In general, when we take the absolute value of a quantity, we can represent it as either itself, or as its additive inverse.

In other words, |x| = x (if x > 0) or |x| = –x (if x < 0).

Therefore, we can represent |4 – 2x| as either 4 – 2x or as –(4 – 2x). We must consider both of these cases and solve for x. Let’s us first consider the case that |4 – 2x| = 4 – 2x.

4 – 2x < 5

We can add 2x to both sides

4 < 2x + 5

Then subtract 5 from both sides.

–1 < 2x

Divide by 2.

–1/2 < x

x > –0.5

Now, we consider the case that |4 – 2x | = –(4 – 2x).

–(4 – 2x) < 5

Multiply both sides by negative one. Remember, whenever we multiply or divide an inequality by a negative number, we must flip the inequality sign.

4 – 2x > –5

Add 2x to both sides.

4 > 2x – 5

Add 5 to both sides.

9 > 2x

Divide by 2,

9/2 > x

4.5 > x

This means that the values of x that satisfy the original quality must be greater than -0.5 AND less than 4.5.

The question asks us to find the sum of the integer values of x that satisfy the inequality. The only integers between -0.5 and 4.5 are the following: 0, 1, 2, 3, and 4.

The sum of 0, 1, 2, 3, and 4 is 10.

The answer is 10.

Example Question #2 : How To Find A Solution Set

How many distinct solutions does the following polynomial have?

x(x– 14+ 49) = 0

Possible Answers:

4

1

3.5

2

3

Correct answer:

2

Explanation:

There are 3 solutions: 0, 7, 7.

The correct answer is 2 distinct solutions, however, because 7 occurs twice.  So the two distinct solutions are 0 and 7.

Example Question #162 : Algebra

Solve x2 – 48 = 0.

Possible Answers:

x = 0

x = 4 or x = –4

x = –√48

x = 4√3

x = 4√3 or x = –4√3

Correct answer:

x = 4√3 or x = –4√3

Explanation:

No common terms cancel out, and this isn't a difference of squares. 

Let's move the 48 to the other side: x2 = 48

Now take the square root of both sides: x = √48 or x = –√48. Don't forget the second (negative) solution! 

Now √48 = √(3*16) = √(3*42) = 4√3, so the answer is x = 4√3 or x = –4√3.

Example Question #1 : Solution Sets

What is the sum of all solutions to the equation

\dpi{100} \small |x+3| = 10\(\displaystyle \dpi{100} \small |x+3| = 10\) ?

Possible Answers:

\dpi{100} \small -13\(\displaystyle \dpi{100} \small -13\)

\dpi{100} \small 14\(\displaystyle \dpi{100} \small 14\)

\dpi{100} \small 13\(\displaystyle \dpi{100} \small 13\)

\dpi{100} \small 7\(\displaystyle \dpi{100} \small 7\)

\dpi{100} \small -6\(\displaystyle \dpi{100} \small -6\)

Correct answer:

\dpi{100} \small -6\(\displaystyle \dpi{100} \small -6\)

Explanation:

If \dpi{100} \small |x+3| = 10\(\displaystyle \dpi{100} \small |x+3| = 10\), then either

\dpi{100} \small x+3 = 10\(\displaystyle \dpi{100} \small x+3 = 10\) or \dpi{100} \small x+3 = -10\(\displaystyle \dpi{100} \small x+3 = -10\).  

These two equations yield \dpi{100} \small 7\(\displaystyle \dpi{100} \small 7\) and \dpi{100} \small -13\(\displaystyle \dpi{100} \small -13\) as answers.  

\dpi{100} \small 7+(-13)=-6\(\displaystyle \dpi{100} \small 7+(-13)=-6\)

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