Holt CA Course 1

1-6 Writing Algebraic Expressions

Mr. Campbell drives at 55 mi/h. Write an algebraic expression for how far he can drive in h hours. Then evaluate the expression for h = 3, and tell what the value of the expression means.

Additional Example 2A: Translating Real-World Problems into Algebraic Expressions

You need to put equal parts together. This involves multiplication.

55mi/h h hours = 55(h) miles

55(h) miles Write the expression.

Substitute 3 for h.55(3) miles

Multiply.165

Mr. Campbell can drive 165 miles in 3 hours.

Holt CA Course 1

1-6 Writing Algebraic Expressions

On a test, multiple-choice questions are worth 1 point, short-answer questions are worth 2 points, and essay questions are worth 10 points. Write an algebraic expression for Maritza’s total points if she answers m multiple-choice, s short-answer, and e essay questions correctly. Then evaluate the expression for m = 48, s = 8, and e = 3, and tell what the value of the expression means.

Additional Example 2B: Translating Real-World Problems into Algebraic Expressions

Multiply to put equal parts together.

multiple-choice questions: 1m or mshort-answer questions: 2s essay questions: 10e

Holt CA Course 1

1-6 Writing Algebraic ExpressionsAdditional Example 2B Continued

Add to put the parts together.

Maritza earned 94 points on the test.

Total points: 1m + 2s + 10e

1m + 2s + 10e Write the expression.

Substitute 48 for m, 8 for s, and 3 for e.

1(48) + 2(8) + 10(3)

Multiply from left to right.48 + 16 + 30

94 Add.

Holt CA Course 1

1-6 Writing Algebraic Expressions

You need to put equal parts together. This involves multiplication.

8(h) units Write the expression.

Substitute 5 for h.8(5) units

Multiply.40

Julie Ann can build 40 units in 5 hours.

Check It Out! Example 2A

Julie Ann works on an assembly line building computers. She can assemble 8 units an hour. Write an expression for the number of units she can produce in h hours. Then evaluate the expression for h = 5, and tell what the value of the expression means.

8 units/h h hours = 8h

Holt CA Course 1

1-6 Writing Algebraic Expressions

For lunch, students have 3 choices. A turkey sandwich for $3, a bowl of soup for $2, and a chicken salad for $4. Write an algebraic expression to show how much it costs for s sandwiches, b bowls of soup, and c chicken salads. Then evaluate the expression for s = 32, b = 20, and c = 10, and tell what the value of the expression means.

Check It Out! Example 2B

Multiply to put equal parts together.

turkey sandwich: 3s

bowls of soup: 2b chicken salad: 4c

Holt CA Course 1

1-6 Writing Algebraic ExpressionsCheck It Out! Example 2B Continued

Add to put equal parts together.

The cost of 32 turkey sandwiches, 20 bowls of soup, and 10 chicken salads is $176.

Total cost: 3s + 2b + 4c

3s + 2b + 4c Write the expression.

Substitute 32 for s, 20 for b, and 10 for c.

3(32) + 2(20) + 4(10)

Multiply from left to right.96 + 40 + 40

176 Add.

Holt CA Course 1

1-6 Writing Algebraic ExpressionsLesson Quiz

Write each phrase as an algebraic expression.

1. 18 less than a number

2. the quotient of a number and 21

3. 8 times the sum of x and 15

4. 7 less than the product of a number and 5

x – 18

8(x + 15)

5n – 7

5. The county fair charges an admission of $6 and then charges $2 for each ride. Write an algebraic expression to represent the total cost after r rides at the fair. 6 + 2r

x21