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Solving Equations by Adding or Subtracting Decimals. PRE-ALGEBRA LESSON 3-5. (For help, go to Skills Handbook page 730.). Simplify. 1. 2.8 + 7.06 2. 0.65 + 1.8 3. 4.52 – 2.48 4. 3.7 – 0.62. Check Skills You’ll Need. 3-5. Solving Equations by Adding or Subtracting Decimals. - PowerPoint PPT Presentation
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Solving Equations by Adding or Subtracting DecimalsSolving Equations by Adding or Subtracting DecimalsPRE-ALGEBRA LESSON 3-5PRE-ALGEBRA LESSON 3-5
(For help, go to Skills Handbook page 730.)
Simplify.
1. 2.8 + 7.06 2. 0.65 + 1.8
3. 4.52 – 2.48 4. 3.7 – 0.62
Check Skills You’ll Need
3-5
Solving Equations by Adding or Subtracting DecimalsSolving Equations by Adding or Subtracting DecimalsPRE-ALGEBRA LESSON 3-5PRE-ALGEBRA LESSON 3-5
Solutions
1. 2.80 2. 0.65 + 7.06 + 1.80
9.86 2.45
3. 4.52 4. 3.70– 2.48 – 0.62
2.04 3.08
3-5
Solve 6.8 + p = –9.7.
Solving Equations by Adding or Subtracting DecimalsSolving Equations by Adding or Subtracting DecimalsPRE-ALGEBRA LESSON 3-5PRE-ALGEBRA LESSON 3-5
6.8 + p = –9.7
6.8 – 6.8 + p = –9.7 – 6.8 Subtract 6.8 from each side.
p = –16.5 Simplify.
Check 6.8 + p = –9.7
6.8 + (–16.5) –9.7 Replace p with –16.5.
–9.7 = –9.7
Quick Check
3-5
Ping has a board that is 14.5 ft long. She saws off a
piece that is 8.75 ft long. Use the diagram below to find the
length of the piece that is left.
Solving Equations by Adding or Subtracting DecimalsSolving Equations by Adding or Subtracting DecimalsPRE-ALGEBRA LESSON 3-5PRE-ALGEBRA LESSON 3-5
The length of the piece that is left is 5.75 ft.
x = 5.75 Simplify.
x + 8.75 – 8.75 = 14.5 – 8.75 Subtract 8.75 from each side.
x + 8.75 = 14.5
Quick Check
3-5
Solve –23.34 = q – 16.99.
Solving Equations by Adding or Subtracting DecimalsSolving Equations by Adding or Subtracting DecimalsPRE-ALGEBRA LESSON 3-5PRE-ALGEBRA LESSON 3-5
–23.34 = q – 16.99
–23.34 + 16.99 = q – 16.99 + 16.99 Add 16.99 to each side.
–6.35 = q Simplify.
Quick Check
3-5
Alejandro wrote a check for $49.98. His new account
balance is $169.45. What was his previous balance?
Solving Equations by Adding or Subtracting DecimalsSolving Equations by Adding or Subtracting DecimalsPRE-ALGEBRA LESSON 3-5PRE-ALGEBRA LESSON 3-5
Alejandro had $219.43 in his account before he wrote the check.
Simplify.p = 219.43
Add 49.98 to each side.p – 49.98 + 49.98 = 169.45 + 49.98
p – 49.98 = 169.45
Equation p – $49.98 = $169.45
Let p = previous balance.
Words previous balance minus check is new balance
Quick Check
3-5
Solving Equations by Adding or Subtracting DecimalsSolving Equations by Adding or Subtracting DecimalsPRE-ALGEBRA LESSON 3-5PRE-ALGEBRA LESSON 3-5
Solve each equation.
1. a + 10 = 7.9 2. –1.01 = c – 9
3. s – (–2.6) = 1.6 4. 3.02 + d = 2.91
5. –23.7 = 13.3 + g
– 37
– 2.1 7.99
– 1 – 0.11
3-5
Every day the school cafeteria uses about 85.8
gallons of milk. About how many days will it take for the
cafeteria to use the 250 gallons in the refrigerator?
Solving Equations by Multiplying or Dividing DecimalsSolving Equations by Multiplying or Dividing DecimalsPRE-ALGEBRA LESSON 3-6PRE-ALGEBRA LESSON 3-6
Let x = number of days.
numberof days
Words times is 250 gallonsdaily milk
consumption
Equation • =85.8 x 250
3-6
(continued)
Solving Equations by Multiplying or Dividing DecimalsSolving Equations by Multiplying or Dividing DecimalsPRE-ALGEBRA LESSON 3-6PRE-ALGEBRA LESSON 3-6
85.8x = 250
The school will take about 3 days to use 250 gallons of milk.
x = 2.914 . . . Simplify.
x 3 Round to the nearest whole number.
85.8x85.8 =
25085.8 Divide each side by 85.8.
Quick Check
3-6
Solve –37.5 = .
Solving Equations by Multiplying or Dividing DecimalsSolving Equations by Multiplying or Dividing DecimalsPRE-ALGEBRA LESSON 3-6PRE-ALGEBRA LESSON 3-6
c–1.2
–37.5 =c
–1.2
Multiply each side by –1.2.–37.5(–1.2) = (–1.2)c
–1.2
45 = c Simplify.
Quick Check
3-6
A little league player was at bat 15 times and had
a batting average of 0.133 (rounded to the nearest thousandth). The
batting average formula is a = , where a is the batting average, h is
the number of hits, and n is the number of times at bat. Use the
formula to find the number of hits she made.
Solving Equations by Multiplying or Dividing DecimalsSolving Equations by Multiplying or Dividing DecimalsPRE-ALGEBRA LESSON 3-6PRE-ALGEBRA LESSON 3-6
hn
a =hn
0.133 =h
15 Replace a with 0.133 and n with 15.
3-6
(continued)
Solving Equations by Multiplying or Dividing DecimalsSolving Equations by Multiplying or Dividing DecimalsPRE-ALGEBRA LESSON 3-6PRE-ALGEBRA LESSON 3-6
0.133(15) = (15)h
15 Multiply each side by 15.
Simplify.1.995 = h
2 h Since h (hits) represents an integer, round to the nearest integer.
The little league player made 2 hits.
Quick Check
3-6
Solving Equations by Multiplying or Dividing DecimalsSolving Equations by Multiplying or Dividing DecimalsPRE-ALGEBRA LESSON 3-6PRE-ALGEBRA LESSON 3-6
Solve each equation.
1. 9b = –30.6 2. –10.8 =
3. 2.45 = –0.7k 4. = 240
5. y ÷ (–0.3) = 146.7
– 44.01
–3.4 27
p–2.5
–3.5
t3.7
888
3-6
