Understanding Inequalities - SAT Mathematics (2024)

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Example Question #1 : Understanding Inequalities

Understanding Inequalities - SAT Mathematics (1)

Which of the following expresses the complete set of values forUnderstanding Inequalities - SAT Mathematics (2)that satisfy the inequality above?

Possible Answers:

Understanding Inequalities - SAT Mathematics (3)

Understanding Inequalities - SAT Mathematics (4)

Understanding Inequalities - SAT Mathematics (5)

Understanding Inequalities - SAT Mathematics (6)

Correct answer:

Understanding Inequalities - SAT Mathematics (7)

Explanation:

Inequalities can be solved just like equations, with one important caveat: if you multiply or divide by a negative number, you have to flip the inequality sign. Here, as you will see, there is no need to do that, so you can solve this just like you would an equation. First, multiply both sides by 2 to eliminate the denominator:

Understanding Inequalities - SAT Mathematics (8)

Next, add 2 to both sides to isolate theUnderstanding Inequalities - SAT Mathematics (9)term:

Understanding Inequalities - SAT Mathematics (10)

Then divide both sides by 3 to getUnderstanding Inequalities - SAT Mathematics (11)alone:

Understanding Inequalities - SAT Mathematics (12)

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Example Question #2 : Understanding Inequalities

Understanding Inequalities - SAT Mathematics (13)

Which of the following represents the complete set of values ofUnderstanding Inequalities - SAT Mathematics (14)that satisfy the inequality above?

Possible Answers:

Understanding Inequalities - SAT Mathematics (15)

Understanding Inequalities - SAT Mathematics (16)

Understanding Inequalities - SAT Mathematics (17)

Understanding Inequalities - SAT Mathematics (18)

Correct answer:

Understanding Inequalities - SAT Mathematics (19)

Explanation:

This problem showcases an important concept about working with inequalities. If you multiply or divide an inequality by a negative number, you must flip the inequality sign. Here you might divide both sides of the original inequality byUnderstanding Inequalities - SAT Mathematics (20)to getUnderstanding Inequalities - SAT Mathematics (21)alone. If you do so, however, you must flip the sign to get:

Understanding Inequalities - SAT Mathematics (22)

You may wish to choose a number consistent with your answer to make sure that it satisfies the original inequality. If you were to chooseUnderstanding Inequalities - SAT Mathematics (23)you would see that the given inequality becomes:Understanding Inequalities - SAT Mathematics (24), which works becauseUnderstanding Inequalities - SAT Mathematics (25)

Note that on many problems it is possible to avoid multiplying/dividing by a negative by adding or subtracting (which have no such restrictions) terms to sides of the inequality where they will be positive. For example, given Understanding Inequalities - SAT Mathematics (26), if you addUnderstanding Inequalities - SAT Mathematics (27)to both sides and subtract 10 from both sides, you'll end up withUnderstanding Inequalities - SAT Mathematics (28), and now you will divide by positive 2, and not have to worry about sign-flipping to arrive atUnderstanding Inequalities - SAT Mathematics (29).

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Example Question #3 : Understanding Inequalities

IfUnderstanding Inequalities - SAT Mathematics (30), then which of the following must be true?

I.Understanding Inequalities - SAT Mathematics (31)

II.Understanding Inequalities - SAT Mathematics (32)

III.Understanding Inequalities - SAT Mathematics (33)

Correct answer:

None of these must be true

Explanation:

At first glance, you might simply multiply both sides of the original inequality byUnderstanding Inequalities - SAT Mathematics (34) and believe that Understanding Inequalities - SAT Mathematics (35). However, what ifUnderstanding Inequalities - SAT Mathematics (36) is a negative number? Remember that when you multiply or divide by a negative number in an inequality, you must flip the sign. But here you don't know whether multiplying by Understanding Inequalities - SAT Mathematics (37)would mean multiplying by a positive number or a negative number, so you don't know which direction the sign should point. An important consideration in manipulating inequalities is that you can never multiply or divide by a variable unless you know the sign of the variable. As a result both I and II are possible but neither is guaranteed:

  1. IfUnderstanding Inequalities - SAT Mathematics (38) is positive thenUnderstanding Inequalities - SAT Mathematics (39)

  2. IfUnderstanding Inequalities - SAT Mathematics (40) is negative then you must flip the sign andUnderstanding Inequalities - SAT Mathematics (41)

  3. The given statement implies that x and y are either both negative or both positive but you do not know which is the case.

As a result, none of these statements “must be true” so the correct answer is "none of these must be true."

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Example Question #4 : Understanding Inequalities

IfUnderstanding Inequalities - SAT Mathematics (42), which of the following must be true?

Possible Answers:

Understanding Inequalities - SAT Mathematics (43)

Understanding Inequalities - SAT Mathematics (44)

Understanding Inequalities - SAT Mathematics (45)

Understanding Inequalities - SAT Mathematics (46)

Correct answer:

Understanding Inequalities - SAT Mathematics (47)

Explanation:

Inequalities can be solved just like equations (with the caveat that if you multiply/divide by a negative you must flip the sign of the inequality, but that does not come in to play on this problem). So you can solve this by doing the same thing to both sides of the inequality. Starting withUnderstanding Inequalities - SAT Mathematics (48), you can:

1) Add 2 to both sides to get:

Understanding Inequalities - SAT Mathematics (49)

2) Divide both sides by 2 to get:

Understanding Inequalities - SAT Mathematics (50)

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Example Question #5 : Understanding Inequalities

Understanding Inequalities - SAT Mathematics (51)

Which of the following represents the full set of values ofUnderstanding Inequalities - SAT Mathematics (52)that satisfy the above inequality?

Possible Answers:

Understanding Inequalities - SAT Mathematics (53)

Understanding Inequalities - SAT Mathematics (54)

Understanding Inequalities - SAT Mathematics (55)

Understanding Inequalities - SAT Mathematics (56)

Correct answer:

Understanding Inequalities - SAT Mathematics (57)

Explanation:

Inequalities can be solved just like equations can, with one important caveat as you'll see in this problem: if you multiply or divide by a negative number, you have to flip the direction of the inequality sign.

Here you can start by multiplying both sides by 2 in order to eliminate the denominator. That brings you to:

Understanding Inequalities - SAT Mathematics (58)

Now you have a choice for how you move the remaining terms to isolate and solve for the variable. If you subtract 6 from both sides, you'll have:

Understanding Inequalities - SAT Mathematics (59)

Here note that in order to solve for the solution set ofUnderstanding Inequalities - SAT Mathematics (60), you would have to divide by -1 to remove the negative. If you do so, you'll need to flip the direction of the sign to get the proper answer:

Understanding Inequalities - SAT Mathematics (61)

Now, also recognize that you could have avoided the divide-by-negative step altogether. At this point:

Understanding Inequalities - SAT Mathematics (62)

You could have addedUnderstanding Inequalities - SAT Mathematics (63)to both sides to get:

Understanding Inequalities - SAT Mathematics (64)

And then when you subtract 8 from both sides you also end up at the correct answer:

Understanding Inequalities - SAT Mathematics (65)

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Example Question #6 : Understanding Inequalities

Understanding Inequalities - SAT Mathematics (66)

Which of the following represents the complete set of values ofUnderstanding Inequalities - SAT Mathematics (67)that satisfy the inequality above?

Possible Answers:

Understanding Inequalities - SAT Mathematics (68)

Understanding Inequalities - SAT Mathematics (69)

Understanding Inequalities - SAT Mathematics (70)

Understanding Inequalities - SAT Mathematics (71)

Correct answer:

Understanding Inequalities - SAT Mathematics (72)

Explanation:

Inequalities can be solved just like equations, with the only caveat that if you multiply or divide by a negative number you have to reverse the sign of the inequality. In this problem, you should not have to take that step.

First here, your goal is to get all theUnderstanding Inequalities - SAT Mathematics (73)terms on one side and the numeric terms on the other. To do so, you can addUnderstanding Inequalities - SAT Mathematics (74)to both sides and subtractUnderstanding Inequalities - SAT Mathematics (75)from both sides to get:

Understanding Inequalities - SAT Mathematics (76)

Now you want to getUnderstanding Inequalities - SAT Mathematics (77)alone, so you can divide both sides byUnderstanding Inequalities - SAT Mathematics (78). This leaves:

Understanding Inequalities - SAT Mathematics (79), or the reduced fractionUnderstanding Inequalities - SAT Mathematics (80).

Note that you can read inequalities from left to right or from right to left, so here "two thirds is greater than Understanding Inequalities - SAT Mathematics (81)" is the same thing as "Understanding Inequalities - SAT Mathematics (82) is less than two-thirds." So you will find the answer written asUnderstanding Inequalities - SAT Mathematics (83).

Note that you might want to test a value close to your inequality to make sure that it works. Since you haveUnderstanding Inequalities - SAT Mathematics (84), you might tryUnderstanding Inequalities - SAT Mathematics (85). If you plug that in to the given inequality you'll see that it does work, returning the true statementUnderstanding Inequalities - SAT Mathematics (86). This helps confirm your answer.

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Example Question #7 : Understanding Inequalities

Understanding Inequalities - SAT Mathematics (87)

Which of the following represents the complete solution set for values ofUnderstanding Inequalities - SAT Mathematics (88)that satisfy the inequality above?

Possible Answers:

Understanding Inequalities - SAT Mathematics (89)

Understanding Inequalities - SAT Mathematics (90)

Understanding Inequalities - SAT Mathematics (91)

Understanding Inequalities - SAT Mathematics (92)

Correct answer:

Understanding Inequalities - SAT Mathematics (93)

Explanation:

A very important consideration when working with inequalities is that whenever you multiply or divide by a negative number, you must flip the inequality sign. Here that means that if you take the (logical) first step of dividing both sides byUnderstanding Inequalities - SAT Mathematics (94), you need to flip the inequality sign from greater-than to less-than, to get:

Understanding Inequalities - SAT Mathematics (95)

Note that you could also handle this by only using addition/subtraction where the rules are exactly the same as with equations. To do that, addUnderstanding Inequalities - SAT Mathematics (96)and subtractUnderstanding Inequalities - SAT Mathematics (97)from both sides of the given inequality.Understanding Inequalities - SAT Mathematics (98)then becomes:

Understanding Inequalities - SAT Mathematics (99)

Then you're dividing by a positive number,Understanding Inequalities - SAT Mathematics (100), to isolateUnderstanding Inequalities - SAT Mathematics (101). This gives youUnderstanding Inequalities - SAT Mathematics (102), matching the right answer determined above.

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Example Question #8 : Understanding Inequalities

Understanding Inequalities - SAT Mathematics (103)

Which of the following inequalities represents thecomplete solution set for values ofUnderstanding Inequalities - SAT Mathematics (104)that satisfy the inequality above?

Possible Answers:

Understanding Inequalities - SAT Mathematics (105)

Understanding Inequalities - SAT Mathematics (106)

Understanding Inequalities - SAT Mathematics (107)

Understanding Inequalities - SAT Mathematics (108)

Correct answer:

Understanding Inequalities - SAT Mathematics (109)

Explanation:

Inequalities can be solved the same way as equations - do the same thing to both sides until you've isolated the variable - with one important exception. If you multiply or divide by a negative number, you must reverse the inequality sign.That situation (as you'll see here) is typically easy to avoid.

Here if you subtractUnderstanding Inequalities - SAT Mathematics (110)from both sides, you can get all theUnderstanding Inequalities - SAT Mathematics (111)terms on one side of the equation, and with a positive coefficient so you do not need to worry about dividing by a negative. That gives you:

Understanding Inequalities - SAT Mathematics (112)

Then addUnderstanding Inequalities - SAT Mathematics (113)to both sides to isolate the variable on the right:

Understanding Inequalities - SAT Mathematics (114)

Divide byUnderstanding Inequalities - SAT Mathematics (115)and you have your answer:

Understanding Inequalities - SAT Mathematics (116), which is the same asUnderstanding Inequalities - SAT Mathematics (117)

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Example Question #9 : Understanding Inequalities

Understanding Inequalities - SAT Mathematics (118)

Which of the following expresses the complete set of values forUnderstanding Inequalities - SAT Mathematics (119)that satisfy the inequality above?

Possible Answers:

Understanding Inequalities - SAT Mathematics (120)

Understanding Inequalities - SAT Mathematics (121)

Understanding Inequalities - SAT Mathematics (122)

Understanding Inequalities - SAT Mathematics (123)

Correct answer:

Understanding Inequalities - SAT Mathematics (124)

Explanation:

In order to tackle this question, we'll want to keep in mind that inequalities follow all the same rules and operations as equations - with one important exception. When we multiply or divide by a negative, we have to flip the inequality sign, as we are basically "flipping" the relationship over 0 on the number line. (A number that is larger when positive becomes "more negative," and thus smaller when negative, and vice versa).

In this case, we start by getting rid of our denominator by multiplying both sides of our inequality by 4

Understanding Inequalities - SAT Mathematics (125)

we can then subtract two from both sides to get to

Understanding Inequalities - SAT Mathematics (126)

and divide both sides by -3, (keeping in mind that we need to flip the sign when we do so!)

Understanding Inequalities - SAT Mathematics (127)

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