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| | 13 Theory slides |
| | 13 Exercises - Grade E - A |
| | Each lesson is meant to take 1-2 classroom sessions |
Mark wants to buy tickets online to play paintball with his friends next weekend. On the website, he finds the following price list.
Two numerical expressions are equivalent if one of the expressions is obtained from the other by applying properties of addition and multiplication. Knowing this, match each expression in the left column with the equivalent expression.
Apart from the Properties of Equality, the properties of addition and multiplication are also heavily used when rewriting and simplifying expressions or equations. Thus, it is convenient to know these properties. The commutative property of each operation will be discussed first.
The order in which two or more terms are added does not affect the value of the sum. In other words, the addends can be written in any order.
a+ b= b+ a
For example, adding 3 to 6 produces the same result as adding 6 to 3. In both cases, the sum is 9. This property also applies to the sum of more than two terms. 4+ 5+ 1 &= 1+ 5+ 4 &⇓ 10 &= 10 ✓
Since the Commutative Property of Addition is an axiom, it does not need a proof.The order in which two or more factors are multiplied does not affect the value of the product. That is, the multiplicands can be written in any order.
a* b = b* a
For example, multiplying 5 by 4 produces the same result as multiplying 4 by 5. In both cases, the product is 20. This property also applies to the product of more than two terms. 3* 2* 6 &= 2* 6 * 3 &⇓ 36 &= 36 ✓
Since the Commutative Property of Multiplication is an axiom, it does not need a proof.As seen, the commutative property says that the order in which two or more terms are added or multiplied will not change the resulting sum or product. Next, the associative property of addition and multiplication will be presented.
The way three or more terms are grouped when added does not affect the value of the sum.
( a+ b)+ c= a+( b+ c)
For example, consider the sum 3+9+4. Grouping 3+9 and adding it to 4 produces the same result as grouping 9+4 and adding it to 3. ( 3+ 9)+ 4&= 3+( 9+ 4) &⇓ 12 + 4 &= 3 + 13 &⇓ 16 &= 16 ✓
Since the Associative Property of Addition is an axiom, it does not need a proof.The way three or more factors are grouped when multiplied does not affect the value of the product.
( a* b)* c= a*( b* c)
For example, consider the product 2* 4* 6. Grouping 2* 4 and multiplying it by 6 produces the same result as grouping 4* 6 and multiplying it by 2. ( 2* 4)* 6&= 2*( 4* 6) &⇓ 8* 6&= 2* 24 &⇓ 48 &= 48 ✓
Since the Associative Property of Multiplication is an axiom, it does not need a proof.Two expressions are equivalent when one of them is obtained by applying properties of addition and multiplication to the other. For each pair of given expressions, determine whether they are equivalent. In the affirmative case, name the property that transforms one expression into the other.
When solving equations, there are instances in which some parts of an expression can be substituted with an equivalent expression. As an example, consider the following equation. 5t + (9-3) = 30 Since 9-3 equals 6, the second term on the left-hand side can be substituted with 6. 5t + (9-3)^6 = 30 ⇓ 5t + 6 = 30 The previous simplification is able thanks to the Substitution Property of Equality, which also guarantees that the resulting equation and the initial are equivalent.
If two real numbers are equal, then one can be substituted for another in any expression.
If a=b, then a can be substituted for b in any expression.
This morning in science class, Tadeo and Magdalena learned how to convert degrees Celsius to Fahrenheit using the following formula. Celsius to Fahrenheit: F = 9/5C+32 Later, while eating lunch in the schoolyard, they saw that the thermometer indicated a temperature of 77^(∘)F. They wondered what the temperature would be in Celsius. To make the conversion, they used the formula they learned in the morning. However, they got different results.
Who is correct?
C= 23
a/c* b = a* b/c
Multiply
Calculate quotient
Add terms
A false statement was obtained, which suggests that Tadeo's answer is not correct. Next, substitute Magdalena's answer.
C= 25
a/c* b = a* b/c
Multiply
Calculate quotient
Add terms
A true statement was obtained, which implies that Magdalena is correct in saying that 77^(∘)F is the same as 25^(∘)C.
In addition to the commutative and associative properties, multiplication has another useful property that helps in the process of simplifying expressions with parentheses. This property is called the Distributive Property.
Multiplying a number by the sum of two or more addends produces the same result as multiplying the number by each addend individually and then adding all the products together.
a( b ± c) &= a* b ± a* c [1ex] ( b ± c) a &= a* b ± a* c
Note that the factor outside the parentheses is multiplied, or distributed, to every term inside. The Distributive Property is used to simplify expressions with parentheses.
Note that, by the Symmetric Property of Equality, the Distributive Property can also be used to take out a common factor in two or more addends. 9x+ 9* 2 = 9(x+2)
In some cases, the right-hand side expression is more useful than the one on the left.When solving equations, sometimes more than one step is needed. Both the number of steps and the operations required depend on the complexity of the given equation. For example, consider the following pair of equations.
rl Equation (I):& 3/2(x-2)+5 = 14 [0.8em] Equation (II):& y+2y-4 = 11-2y
The general idea is to simplify both sides of the equation and then isolate the variable on one side of the equation. This is usually done by collecting all the variable terms on one side of the equations and combining them. Then, the operations applied to the variable are undone in reverse order.
Equation (I) contains a fraction and parentheses. 3/2(x-2)+5=14
Distribute 3/2
a/2* 2 = a
Add terms
The coefficient of the variable is a fraction. The Multiplication Property of Equality can be used to multiply both sides of the equation by the reciprocal of the coefficient.
LHS * 2/3=RHS* 2/3
Commutative Property of Multiplication
a/b* b/a=1
1* a=a
a*b/c= a* b/c
Multiply
Calculate quotient
As such, x=8 is the solution of Equation (I).
In this equation, the variable is on both sides of the equation. y+2y-4=11-2y Solving the equation will require the additional step of collecting the variables on one side of the equation.
LHS+2y=RHS+2y
Commutative Property of Addition
Add terms
LHS+4=RHS+4
Add terms
.LHS /5.=.RHS /5.
Calculate quotient
In conclusion, y=3 is the solution of Equation (II).
At Ali's fruit store, strawberries are on sale! Today they are $0.60 cheaper per pound than usual. Magdalena stopped at the store on her way home from school and bought eight pounds of strawberries. She paid a total of $14.40.
Special price = Usual price - 0.60 ⇓ Special price = x - 0.60 With this special price, Magdalena paid $14.40 for eight pounds of strawberries. Consequently, 8 multiplied by the special price is equal to the total amount paid. Using this information, an equation in terms of x can be established. ( c Number of pounds ) ( c Special price ) = c Total paid ⇓ 8( x - 0.60) = 14.40 This equation can be used to determine the usual price of a pound of strawberries.
8(x-0.60) = 14.40 First, apply the Distributive Property to clear the parentheses. Then, apply the Properties of Equality to isolate the x variable.
Distribute 8
Multiply
LHS+4.8=RHS+4.8
.LHS /8.=.RHS /8.
Calculate quotient
This means that the usual price of one pound of strawberries is $ 2.40. To find how much Tadeo paid, multiply 6 — the number of pounds he bought — by the usual price.
Consequently, last week Tadeo paid $14.40 for six pounds of strawberries. Note that Tadeo paid the same as Magdalena, but he bought 2 pounds fewer.
After dinner, Magdalena works on a 3D model of a castle using cardboard for a history project. She wants the walls of the ramparts to be 7 inches wide. Additionally, she wants the value of the perimeter of the wall, in inches, to be the same as the value of its area, in square inches.
How high should the wall be?
The right-hand side of the wall has the same length as the left-hand side of the wall — that is, both have a length of x inches. Adding these two lengths to the base length, 7 inches, and to the length of the top of the wall, the perimeter of the wall will be obtained.
Top Length= 11
Commutative Property of Addition
Associative Property of Addition
Add terms
To find the wall's area, note that it is made by cutting two small rectangles from the bigger rectangle, whose dimensions are 7 by x.
Consequently, the wall's area is equal to the area of the big rectangle minus the area of the two small rectangles. The big rectangle area is 7x, and the area of each small rectangle is 2 square inches.
A_(Big)= 7x, A_(Small)= 2
Multiply
Since the perimeter and area of the wall must be the same, equate P and A. P &= A &⇓ 2x+18 &= 7x - 4 To find the wall's height, solve the equation for x. Since the equation has variables on both sides, start by collecting them on one side of the equation.
LHS-2x=RHS-2x
Commutative Property of Addition
Subtract terms
LHS+4=RHS+4
Add terms
.LHS /5.=.RHS /5.
Calculate quotient
Rearrange equation
Therefore, the wall should be 4.4 inches high.
Solve the given equation for the indicated variable. If necessary, round the answer to two decimal places.
At the beginning of the lesson, Mark was buying some paintball tickets. He found the following prices online, where the $4 service charge is per transaction, not per ticket.
| Course 1 | |
|---|---|
| Ticket price | $15.00 |
| Processing fee per ticket | $1.50 |
| Service charge | $4.00 |
Let t be the number of purchased tickets. Then, the amount paid only for the tickets without any fees will be the product of 15 and t. 15t Since the group did not get a discount, they paid the processing fee for all the tickets bought. To find the amount paid only in fees, multiply the price of the processing fee by t. 1.5t They also had to pay a service charge, which is $4 no matter the number of tickets bought. The sum of the three costs together will give an expression representing the total cost of purchasing t tickets for Course 1. 15t+1.5t+4 Finally, it is said that they paid a total of $103. Therefore, equate the previous expression to 103.
15t+1.5t+4 = 103
This equation models the situation in which Mark and his friends chose Course 1, got no discount, and paid $103.
| Course 2 | |
|---|---|
| Ticket price | $18.00 |
| Processing fee per ticket | $1.50 |
| Service charge | $4.00 |
Let t be the number of purchased tickets. Since the price per ticket is $18.00, the amount paid only for the tickets — without any fees — will be the product of the price per ticket and t. 18t Since the group received a discount this time, they did not pay the fee for five of the tickets bought. Thus, to find the amount paid in fees, multiply the processing fee by (t-5). 1.5(t-5) They also paid a service charge, which is $4 no matter the number of tickets bought. By adding the three costs, an expression representing the money paid for the purchase of t tickets for Course 2 will be found. 18t+1.5(t-5)+4 Finally, it is said that they paid a total of $230.50. Therefore, equate the previous expression to 230.5.
18t+1.5(t-5)+4 = 230.5
This equation models the situation in which Mark and his friends chose Course 2, got a discount, and paid $230.50.
Associative Property of Addition
Add terms
LHS-4=RHS-4
.LHS /16.5.=.RHS /16.5.
Calculate quotient
Consequently, the first time Mark bought 6 tickets. This confirms why he did not get the discount. To find the number of tickets he bought the second time, the equation set in Part B will be solved for t.
Distribute 1.5
Multiply
Commutative Property of Addition
Associative Property of Addition
Add and subtract terms
a+(- b)=a-b
LHS+3.5=RHS+3.5
.LHS /19.5.=.RHS /19.5.
Calculate quotient
In conclusion, Mark bought 12 tickets the second time.
To make the tower of a cardboard castle, Zosia needs to cut out a triangle and a rectangle, both with the same area, whose dimensions are shown in the figure.
What is the area of the triangle?
The area of a triangle is half the product of its base and its height. Let's start by writing an expression that represents the area of the triangle that Zosia needs. Triangle's Area [0.15cm] 1/2x* 40 = 40x/2 We need to know the value of x in order to calculate the area of the triangle. To find it, let's also write an expression representing the area of the rectangle that Zosia needs. We will use the fact that the area of a rectangle is equal to the length multiplied by the width. Rectangle's Area 12.5(x+18) Since the triangle and the rectangle have the same area, we can equate the expressions so that we get an equation in terms of x. 40x/2 = 12.5(x+18) We can find the value of x by solving the equation. To start, let's multiply both sides of the equation by 2 to get rid of the fractions.
Next, we can distribute 25 to clear all the parentheses.
Finally, we will group the variable terms on the left-hand side. We can then apply inverse operations to isolate x.
The value of x is 30, which means that the base of the triangle is 30 millimeters long. Knowing this, we can find the area of the triangle.
The area of the triangle is 600 square millimeters. Since the triangle and the rectangle have the same area, we could also substitute x=30 into the expression representing the area of the rectangle — we would get the same answer, though.
Four consecutive even numbers add up to 92. What is the next even number?
To determine the next even number, we need to find the value of the four consecutive even numbers. Let's start by calling the smallest of the four even numbers x. \begin{gathered} \bm{1}^\text{st} \to {\color{#0000FF}{x}} \end{gathered} Since the four numbers are even and consecutive, the second even number is two units greater than x. This means that we can write it as x+2. \begin{aligned} \bm{1}^\text{st} &\to {\color{#0000FF}{x}} \\ \bm{2}^\text{nd} &\to {\color{#009600}{x+2}} \end{aligned} The third even number is two units greater than the second one. Then, the third number equals x+2+2, which is the same as x+4. \begin{aligned} \bm{1}^\text{st} &\to {\color{#0000FF}{x}} \\ \bm{2}^\text{nd} &\to {\color{#009600}{x+2}} \\ \bm{3}^\text{rd} &\to {\color{#FD9000}{x+4}} \end{aligned} Similarly, the fourth even number is two units greater than the third one. Therefore, the fourth number equals x+4+2, or x+6. \begin{aligned} \bm{1}^\text{st} &\to {\color{#0000FF}{x}} \\ \bm{2}^\text{nd} &\to {\color{#009600}{x+2}} \\ \bm{3}^\text{rd} &\to {\color{#FD9000}{x+4}} \\ \bm{4}^\text{th} &\to {\color{#A800DD}{x+6}} \end{aligned} Now that we have expressions for each of the four consecutive even numbers in terms of x, we can add them and equate the sum to 92. x + ( x+2) + ( x+4) + ( x+6) = 92 We can find the value of x by solving the equation. Note that the equation has no fractions and the variable terms are all grouped on the left-hand side. This means that we can simply combine like terms and isolate the variable through inverse operations to solve the equation.
The value of x is 20, so the smallest of the four consecutive even numbers is 20. Knowing this, we can determine the next three even numbers. \begin{aligned} \bm{1}^\text{st} &\to {\color{#0000FF}{20}} \\ \bm{2}^\text{nd} &\to {\color{#009600}{22}} \\ \bm{3}^\text{rd} &\to {\color{#FD9000}{24}} \\ \bm{4}^\text{th} &\to {\color{#A800DD}{26}} \end{aligned} We can conclude that the fifth even number is 26+2=28.
In a triangle ABC, the side AB is 3 centimeters shorter than BC, and AC is twice as long as AB. If the perimeter of the triangle is 23 centimeters, what is the length of the longest side of the triangle?
To determine the length of the longest side of the triangle, we need to know its three side lengths. Let's try to write expressions representing the side lengths in terms of one variable. To start, we can call x the length of BC. BC → x We are told that AB is 3 centimeters shorter than BC, which allows us to write the length of AB in terms of x. ABis3centimeters shorter thanBC ⇓ AB → x-3 Also, we know that AC is twice as long as AB. This means that the length of AC is 2 times the length of AB. ACis twice as long asAB ⇓ AC → 2(x-3) Now we have the side lengths written in terms of only one variable. The perimeter of a triangle equals the sum of the three side lengths. We know that the perimeter of △ ABC is 23 centimeters. Therefore, the sum of the three expressions is equal to 23. x + x-3 + 2(x-3) = 23 Next, let's solve the equation for x. We will start by distributing 2 to clear all the parentheses and continue by combining like terms.
Finally, we isolate the variable on the left-hand side by applying inverse operations.
The value of x is 8. This means that BC is 8 centimeters long. Knowing this, the other two side lengths can be calculated. BC & → 8 cm AB & → 8-3 = 5 cm AC & → 2(8-3) = 10 cm As we can see, the longest side of △ ABC is AC, which is 10 centimeters long.
The following figure is made of four identical rectangles and one square whose area is half the area of a rectangle.
If the area of the figure is 54 square inches, what is the area of one of the rectangles?
We are told that the figure is made of four identical rectangles and one square. Let x be the area of each rectangle. Since the area of the square is half the area of a rectangle, the area of the square is 12x. Rectangle's Area &→ x [0.3em] Square's Area &→ 1/2x There are four rectangles in the figure and the area of all of them together is 4x. We can find the total area of the figure by adding together the area of the four rectangles and the area of the square. We also know that this area is 54 square inches, so we will set this expression equal to 54. 4x + 1/2x = 54 Let's solve the equation to find the value of x. To start, we will multiply both sides of the equation by 2 to get rid of the fraction. Then, we will combine like terms and isolate the variable using inverse operations.
The area of each rectangle is 12 square inches. This means that the area of the square is 6 square inches.