Warm Up Problem of the Day Lesson Presentation Lesson Quizzes

Warm Up Solve. 1. x – 3 = 11 2. 18 = x + 4 x = 14 3. = 42 4. 2x = 52 3. = 42 4. 2x = 52 5. x – 82 = 172 x = 14 x = 14 x x = 294 7 x = 26 x = 254

Problem of the Day Find the missing entries in the magic square. 11.25 is the sum of every row, column, and diagonal. 3.75 5.25 6 3 6.75 1.5 2.25 0.75 4.5

Learn to solve equations involving decimals.

You can solve equations with decimals using inverse operations just as you solved equations with whole numbers. $45.20 + m = $69.95 –$45.20 –$45.20 m = $24.75

Use inverse operations to get the variable alone on one side of the equation. Remember!

Additional Example 1A: Solving One-Step Equations with Decimals Solve the equation. Check your answer. k – 6.2 = 9.5 k – 6.2 = 9.5 6.2 is subtracted from k. + 6.2 + 6.2 Add 6.2 to both sides to undo the subtraction. k = 15.7 Check k – 6.2 = 9.5 Substitute 15.7 for k in the equation. 15.7 – 6.2 = 9.5 ? 9.5 = 9.5 ?  15.7 is the solution.

Additional Example 1B: Solving One-Step Equations with Decimals Solve the equation. Check your answer. 6k = 7.2 k is multiplied by 6. 6k = 7.2 6k = 7.2 Divide both sides by 6 to undo the multiplication. 6 6 k = 1.2 Check 6k = 7.2 Substitute 1.2 for k in the equation. 6(1.2) = 7.2 ? 7.2 = 7.2 ?  1.2 is the solution.

Additional Example 1C: Solving One-Step Equations with Decimals Solve the equation. Check your answer. m = 0.6 m is divided by 7. 7 m 7 · 7 = 0.6 · 7 Multiply both sides by 7 to undo the division. m = 4.2 Check = 0.6 m 7 Substitute 4.2 for m in the equation. = 0.6 4.2 7 ? 0.6 = 0.6 ?  4.2 is the solution.

Solve the equation. Check your answer. Check It Out: Example 1A Solve the equation. Check your answer. n – 3.7 = 8.6 n – 3.7 = 8.6 3.7 is subtracted from n. + 3.7 + 3.7 Add 3.7 to both sides to undo the subtraction. n = 12.3 Check n – 3.7 = 8.6 Substitute 12.3 for n in the equation. 12.3 – 3.7 = 8.6 ? 8.6 = 8.6 ?  12.3 is the solution.

Solve the equation. Check your answer. Check It Out: Example 1B Solve the equation. Check your answer. 7h = 8.4 h is multiplied by 7. 7h = 8.4 7h = 8.4 Divide both sides by 7 to undo the multiplication. 7 7 h = 1.2 Check 7h = 8.4 Substitute 1.2 for h in the equation. 7(1.2) = 8.4 ? 8.4 = 8.4 ?  1.2 is the solution.

Solve the equation. Check your answer. Check It Out: Example 1C Solve the equation. Check your answer. w = 0.3 w is divided by 9. 9 w 9 · 9 = 0.3 · 9 Multiply both sides by 9 to undo the division. w = 2.7 Check = 0.3 w 9 Substitute 2.7 for w in the equation. = 0.3 2.7 9 ? 0.3 = 0.3 ?  2.7 is the solution.

The area of a rectangle is its length times its width. A = lw Remember! w l

Additional Example 2A: Measurement Application The area of Emily’s floor is 33.75 m2. If its length is 4.5 meters, what is its width? area = length · width 33.75 = 4.5 · w Write the equation for the problem. Let w be the width of the room. 33.75 = 4.5w 33.75 = 4.5w Divide both sides by 4.5 to undo the multiplication. 4.5 4.5 7.5 = w The width of Emily’s floor is 7.5 meters.

Additional Example 2B: Measurement Application If carpet costs $23 per square meter, what is the total cost to carpet the floor? total cost = area · cost of carpet per square meter Let C be the total cost. Write the equation for the problem. C = 33.75 · 23 C = 776.25 Multiply. The cost of carpeting the floor is $776.25.

Check It Out: Example 2A The area of Yvonne’s bedroom is 181.25 ft2. If its length is 12.5 feet, what is its width? area = length · width 181.25 = 12.5 · w Write the equation for the problem. Let w be the width of the room. 181.25 = 12.5w 181.25 = 12.5w Divide both sides by 12.5 to undo the multiplication. 12.5 12.5 14.5 = w The width of Yvonne’s bedroom is 14.5 feet.

Check It Out: Example 2B If carpet costs $4 per square foot, what is the total cost to carpet the bedroom? total cost = area · cost of carpet per square foot Let C be the total cost. Write the equation for the problem. C = 181.25 · 4 C = 725 Multiply. The cost of carpeting the bedroom is $725.