PSAT Math : Algebra

Study concepts, example questions & explanations for PSAT Math

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Example Questions

Example Question #2 : Inequalities

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

what is a possible value for x?

Possible Answers:

–8

10

11

–10

0

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 #2 : Inequalities

Solve for x.

-2x+5\leq 10

Possible Answers:

x\geq \frac{5}{2}

x\leq 5

None\ of\ the\ above

x\leq \frac{5}{2}

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 #3 : 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:

III only

II only

I only

I and 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 #1 : 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.

Example Question #11 : New Sat Math Calculator

\dpi{100} \small -2y+7>-7+y

Given the inequality above, which of the following MUST be true?

Possible Answers:

\dpi{100} \small y>\frac{14}{3}

\dpi{100} \small y>\frac{-14}{3}

\dpi{100} \small y<5

\dpi{100} \small y<\frac{-14}{3}

\dpi{100} \small y>-5

Correct answer:

\dpi{100} \small y>-5

Explanation:

\dpi{100} \small -2y+7>-7+ySubtract  from both sides:

Subtract 7 from both sides:

Divide both sides by \dpi{100} \small -3:

Remember to switch the inequality when dividing by a negative number:

Since \dpi{100} \small y<\frac{14}{3} is not an answer, we must find an answer that, at the very least, does not contradict the fact that  is less than (approximately) 4.67.  Since any number that is less than 4.67 is also less than any number that is bigger than 4.67, we can be sure that  is less than 5.

Example Question #1 : Inequalities

A factory packs cereal boxes. Before sealing each box, a machine weighs it to ensure that it is no lighter than 356 grams and no heavier than 364 grams. If the box holds  grams of cereal, which inequality represents all allowable values of ?

Possible Answers:

Correct answer:

Explanation:

The median weight of a box of cereal is 360 grams. This should be an allowable value of w. Substituting 360 for w into each answer choice, the only true results are:

and:

Notice that any positive value for w satisfies the second inequality above. Since w must be between 356 and 364, the first inequality above is the only reasonable choice.

Example Question #431 : Algebra

What values of x make the following statement true?

|x – 3| < 9

Possible Answers:

6 < x < 12

x < 12

–3 < x < 9

–6 < x < 12

–12 < x < 6

Correct answer:

–6 < x < 12

Explanation:

Solve the inequality by adding 3 to both sides to get x < 12.  Since it is absolute value, x – 3 > –9 must also be solved by adding 3 to both sides so: x > –6 so combined.

Example Question #432 : Algebra

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

Possible Answers:

w2

w/2

3w/2

|w|0.5

|w|

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 #51 : Equations / Inequalities

Solve for .

Possible Answers:

Correct answer:

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.

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