PSAT Math : Inequalities

Study concepts, example questions & explanations for PSAT Math

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Example Questions

Example Question #4 : How To Find The Solution To An Inequality With Addition

If –1 < w < 1, all of the following must also be greater than –1 and less than 1 EXCEPT for which choice?

Possible Answers:

w/2

w2

|w|

3w/2

|w|0.5

Correct answer:

3w/2

Explanation:

3w/2 will become greater than 1 as soon as w is greater than two thirds. It will likewise become less than –1 as soon as w is less than negative two thirds. All the other options always return values between –1 and 1.

Example Question #5 : How To Find The Solution To An Inequality With Addition

Solve for \displaystyle z.

\displaystyle \left | z-3 \right |\geq 5

Possible Answers:

\displaystyle -2\leq z\leq 8

\displaystyle z\leq -2\ \text{or}\ z\geq 8

\displaystyle -3\leq z\leq 5

\displaystyle z\leq -3\ \text{or}\ z\geq 5

\displaystyle z\geq 8

Correct answer:

\displaystyle z\leq -2\ \text{or}\ z\geq 8

Explanation:

Absolute value problems always have two sides: one positive and one negative.

First, take the problem as is and drop the absolute value signs for the positive side: z – 3 ≥ 5. When the original inequality is multiplied by –1 we get z – 3 ≤ –5.

Solve each inequality separately to get z ≤ –2 or z ≥ 8 (the inequality sign flips when multiplying or dividing by a negative number).

We can verify the solution by substituting in 0 for z to see if we get a true or false statement. Since –3 ≥ 5 is always false we know we want the two outside inequalities, rather than their intersection.

Example Question #6 : How To Find The Solution To An Inequality With Addition

If x+1< 4\displaystyle x+1< 4 and y-2<-1\displaystyle y-2< -1 , then which of the following could be the value of \displaystyle x+y?

Possible Answers:

\displaystyle 8

\displaystyle 16

\displaystyle 12

\displaystyle 0

\displaystyle 4

Correct answer:

\displaystyle 0

Explanation:

To solve this problem, add the two equations together:

x+1<4\displaystyle x+1< 4

y-2<-1\displaystyle y-2< -1

x+1+y-2<4-1\displaystyle x+1+y-2< 4-1

x+y-1<3\displaystyle x+y-1< 3

x+y<4\displaystyle x+y< 4

The only answer choice that satisfies this equation is 0, because 0 is less than 4.

Example Question #3 : How To Find The Solution To An Inequality With Addition

If \displaystyle 17-x>19, which of the following could be a value of \displaystyle x?

Possible Answers:

\displaystyle 2

\displaystyle 4

\displaystyle -4

\displaystyle 0

-\displaystyle -2

Correct answer:

\displaystyle -4

Explanation:

In order to solve this inequality, you must isolate \displaystyle x on one side of the equation. 

\displaystyle 17-x>19

\displaystyle 17 > 19 +x

\displaystyle -2 > x

Therefore, the only option that solves the inequality is \displaystyle -4

 

Example Question #7 : How To Find The Solution To An Inequality With Addition

What values of \displaystyle x make the statement \displaystyle \left |5x-9 \right |\geq6 true?

Possible Answers:

\displaystyle x\geq5,x\leq \frac{1}{5}

\displaystyle x\geq6,x\leq \frac{1}{3}

\displaystyle x\geq4,x\leq -\frac{1}{2}

\displaystyle x\geq15,x\leq \frac{2}{5}

\displaystyle x\geq3, x\leq \frac{3}{5}

Correct answer:

\displaystyle x\geq3, x\leq \frac{3}{5}

Explanation:

First, solve the inequality \displaystyle 5x-9 \geq6:

\displaystyle 5x-9 \geq6

\displaystyle 5x\geq15

\displaystyle x\geq3

Since we are dealing with absolute value, \displaystyle 5x-9\leq-6 must also be true; therefore:

\displaystyle 5x-9\leq-6

\displaystyle 5x\leq3

\displaystyle x\leq \frac{3}{5}

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

If –1 < n < 1, all of the following could be true EXCEPT:

Possible Answers:

(n-1)2 > n

n2 < n

|n2 - 1| > 1

16n2 - 1 = 0

n2 < 2n

Correct answer:

|n2 - 1| > 1

Explanation:

N_part_1

N_part_2

N_part_3

N_part_4

N_part_5

Example Question #181 : Equations / Inequalities

(√(8) / -x ) <  2. Which of the following values could be x?

Possible Answers:

All of the answers choices are valid.

-4

-1

-3

-2

Correct answer:

-1

Explanation:

The equation simplifies to x > -1.41. -1 is the answer.

Example Question #51 : New Sat Math Calculator

Solve for x

\small 3x+7 \geq -2x+4\displaystyle \small 3x+7 \geq -2x+4

 

Possible Answers:

\small x \geq \frac{3}{5}\displaystyle \small x \geq \frac{3}{5}

\small x \leq -\frac{3}{5}\displaystyle \small x \leq -\frac{3}{5}

\small x \leq \frac{3}{5}\displaystyle \small x \leq \frac{3}{5}

\small x \geq -\frac{3}{5}\displaystyle \small x \geq -\frac{3}{5}

Correct answer:

\small x \geq -\frac{3}{5}\displaystyle \small x \geq -\frac{3}{5}

Explanation:

\small 3x+7 \geq -2x+4\displaystyle \small 3x+7 \geq -2x+4

\small 3x \geq -2x-3\displaystyle \small 3x \geq -2x-3

\small 5x \geq -3\displaystyle \small 5x \geq -3

\small x\geq -\frac{3}{5}\displaystyle \small x\geq -\frac{3}{5}

Example Question #2 : How To Find The Solution To An Inequality With Multiplication

We have \displaystyle x^2-4< 0, find the solution set for this inequality. 

Possible Answers:

\displaystyle -2< x< 2

\displaystyle x=0

\displaystyle x< 2

\displaystyle x>2, x< -2

\displaystyle x>-2

Correct answer:

\displaystyle -2< x< 2

Explanation:

\displaystyle x^2-4< 0 \Rightarrow x^2< 4 \Rightarrow -2< x< 2

Example Question #61 : Equations / Inequalities

Fill in the circle with either <\displaystyle < , >\displaystyle >, or =\displaystyle = symbols:

(x-3)\circ\frac{x^2-9}{x+3}\displaystyle (x-3)\circ\frac{x^2-9}{x+3} for x\geq 3\displaystyle x\geq 3.

 

Possible Answers:

(x-3)< \frac{x^2-9}{x+3}\displaystyle (x-3)< \frac{x^2-9}{x+3}

The rational expression is undefined.

(x-3)=\frac{x^2-9}{x+3}\displaystyle (x-3)=\frac{x^2-9}{x+3}

None of the other answers are correct.

(x-3)> \frac{x^2-9}{x+3}\displaystyle (x-3)> \frac{x^2-9}{x+3}

Correct answer:

(x-3)=\frac{x^2-9}{x+3}\displaystyle (x-3)=\frac{x^2-9}{x+3}

Explanation:

(x-3)\circ\frac{x^2-9}{x+3}\displaystyle (x-3)\circ\frac{x^2-9}{x+3}

Let us simplify the second expression. We know that:

(x^2-9)=(x+3)(x-3)\displaystyle (x^2-9)=(x+3)(x-3)

So we can cancel out as follows:

\frac{x^2-9}{x+3}=\frac{(x+3)(x-3)}{(x+3)}=x-3\displaystyle \frac{x^2-9}{x+3}=\frac{(x+3)(x-3)}{(x+3)}=x-3

(x-3)=\frac{x^2-9}{x+3}\displaystyle (x-3)=\frac{x^2-9}{x+3}

 

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