Algebra 1 : Writing inequalities

Study concepts, example questions & explanations for Algebra 1

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Example Questions

Example Question #81 : Expressions & Equations

Write the inequality:  A number less than three is less than three.

Possible Answers:

\(\displaystyle 3-x>3\)

\(\displaystyle x-3>3\)

\(\displaystyle x-3< 3\)

\(\displaystyle x-3< 3-x\)

\(\displaystyle 3-x< 3\)

Correct answer:

\(\displaystyle 3-x< 3\)

Explanation:

Let a number be \(\displaystyle x\).  Split up the problem into parts.

A number less than three:  \(\displaystyle 3-x\)

Is less than three:  \(\displaystyle < 3\)

Combine all the terms.

The answer is:  \(\displaystyle 3-x< 3\)

Example Question #82 : Expressions & Equations

Write the inequality:  Two more than three times a number is more than six.

Possible Answers:

\(\displaystyle 3y+2>6\)

\(\displaystyle 3(y+2)< 6\)

\(\displaystyle 3y+2>6+2\)

\(\displaystyle 3y+2< 6\)

\(\displaystyle 3(y+2)>6\)

Correct answer:

\(\displaystyle 3y+2>6\)

Explanation:

Split up the sentence into parts.  Let the number be \(\displaystyle y\).

Two more than three times a number:  \(\displaystyle 3y+2\)

More than six:  \(\displaystyle >6\)

Combine the parts to form an inequality.

The answer is:  \(\displaystyle 3y+2>6\)

Example Question #11 : Solve Word Problems Leading To Inequalities: Ccss.Math.Content.7.Ee.B.4b

Write the inequality:  A number less than three is greater than five.

Possible Answers:

\(\displaystyle x>\pm2\)

\(\displaystyle x-3< 5\)

\(\displaystyle 3-x>5\)

\(\displaystyle 3-x< 5\)

\(\displaystyle x-3>5\)

Correct answer:

\(\displaystyle 3-x>5\)

Explanation:

Break up the terms and rewrite by parts.

A number less than three:  \(\displaystyle 3-x\)

Greater than five:  \(\displaystyle >5\)

Combine the terms.

The answer is:  \(\displaystyle 3-x>5\)

Example Question #84 : Expressions & Equations

Write the following inequality:  Two less than three times a number is less than four.

Possible Answers:

\(\displaystyle 3x-2 \leq 4\)

\(\displaystyle 3x-2< 4\)

\(\displaystyle 2-3x\leq4\)

\(\displaystyle -2-3x< 4\)

\(\displaystyle 2-3x< 4\)

Correct answer:

\(\displaystyle 3x-2< 4\)

Explanation:

Break up the statement into parts.  Let \(\displaystyle x\) be the number.

Three times a number:  \(\displaystyle 3x\)

Two less than three times a number:  \(\displaystyle 3x-2\)

Less than four:  \(\displaystyle < 4\)

Combine the terms.

The answer is:  \(\displaystyle 3x-2< 4\)

Example Question #85 : Expressions & Equations

Write the inequality:  Twice a number less than six is more than four.

Possible Answers:

\(\displaystyle 2x-6< 4\)

\(\displaystyle 2x-6>4\)

\(\displaystyle 2(x-6)>4\)

\(\displaystyle 6-2x>4\)

\(\displaystyle 6-2x< 4\)

Correct answer:

\(\displaystyle 6-2x>4\)

Explanation:

Break up the inequality into parts.  Let a variable be the number.

Twice a number:  \(\displaystyle 2x\)

Twice a number less than six:  \(\displaystyle 6-2x\)

Is more than four:  \(\displaystyle >4\)

Combine the terms.

The answer is:  \(\displaystyle 6-2x>4\)

Example Question #91 : Expressions & Equations

Write the inequality:  One less than twice the difference of five and twice a number is less than four.

Possible Answers:

\(\displaystyle 4x-6< 4\)

\(\displaystyle 2(2x-5)-1< 4\)

\(\displaystyle 1-2(5-2x)< 4\)

\(\displaystyle 1-2(2x-5)< 4\)

\(\displaystyle 2(5-2x)-1< 4\)

Correct answer:

\(\displaystyle 2(5-2x)-1< 4\)

Explanation:

In order to write this inequality, we need to break up the statement into parts.

Let the number be a random variable.

The difference of five and twice a number:  \(\displaystyle 5-2x\)

Twice the difference of five and twice a number:  \(\displaystyle 2(5-2x)\)

One less than twice the difference of five and twice a number:  \(\displaystyle 2(5-2x)-1\)

Is less than four:  \(\displaystyle < 4\)

Combine the terms.

The answer is:  \(\displaystyle 2(5-2x)-1< 4\)

Example Question #92 : Expressions & Equations

Write the following inequality:  Five times a number less than five is less than negative five.

Possible Answers:

\(\displaystyle 5(x-5)< -5\)

\(\displaystyle 5x-5>-5\)

\(\displaystyle 5-5x< -5\)

\(\displaystyle 5-5x>-5\)

\(\displaystyle 5x-5< -5\)

Correct answer:

\(\displaystyle 5-5x< -5\)

Explanation:

Convert each part of the sentence into mathematical expressions.  Let a random variable be the number.

Five times a number:  \(\displaystyle 5x\)

Five times a number less than five:  \(\displaystyle 5-5x\)

Is less than negative five:  \(\displaystyle < -5\)

Combine the expressions.

The answer is:  \(\displaystyle 5-5x< -5\)

Example Question #93 : Expressions & Equations

Write the inequality:  Two less than eight times a number is at least seven.

Possible Answers:

\(\displaystyle 2-8x\geq7\)

\(\displaystyle 8x-2\geq7\)

\(\displaystyle 8x-2>7\)

\(\displaystyle 2-8x>7\)

\(\displaystyle 8x-2=7\)

Correct answer:

\(\displaystyle 8x-2\geq7\)

Explanation:

Let a number be \(\displaystyle x\).  Break up the sentence to parts.

Eight times a number:  \(\displaystyle 8x\)

Two less than eight times a number: \(\displaystyle 8x-2\)

Is at least seven:  \(\displaystyle \geq7\)

Combine the terms.

The answer is:  \(\displaystyle 8x-2\geq7\)

Example Question #94 : Expressions & Equations

Write the inequality:  Eight more than two times a number is more than two.

Possible Answers:

\(\displaystyle 2x+8\geq2\)

\(\displaystyle 2x+8>2\)

\(\displaystyle 2(x+8)< 2\)

\(\displaystyle 2x+8< 2\)

\(\displaystyle 2(x+8)>2\)

Correct answer:

\(\displaystyle 2x+8>2\)

Explanation:

Split the problem statement into parts.

Two times a number:  \(\displaystyle 2x\)

Eight more than two times a number:  \(\displaystyle 2x+8\)

Is more than two:  \(\displaystyle >2\)

Combine the terms to make an equation.

The answer is:  \(\displaystyle 2x+8>2\)

Example Question #12 : Solve Word Problems Leading To Inequalities: Ccss.Math.Content.7.Ee.B.4b

Write the inequality:  Seven more than a number is less than five.

Possible Answers:

\(\displaystyle 7x>5\)

\(\displaystyle x+7< 5\)

\(\displaystyle x+7>5\)

\(\displaystyle 7>x-5\)

\(\displaystyle 7x< 5\)

Correct answer:

\(\displaystyle x+7< 5\)

Explanation:

Split the statement into parts.

Seven more than a number: \(\displaystyle x+7\)

Is less than five:  \(\displaystyle < 5\)

Combine both parts to form an inequality.

The answer is:  \(\displaystyle x+7< 5\)

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