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| | 16 Theory slides |
| | 10 Exercises - Grade E - A |
| | Each lesson is meant to take 1-2 classroom sessions |
Dominika and her friends are playing a tabletop role playing game that they created. There are three different type of coins in the game — copper, silver, and gold.
Each type of coin has a different value. The least valuable coin is the copper one. A gold coin is worth 4 copper coins and a silver coin is worth 2 copper coins. Wondering how many copper coins x gold coins and y silver coins are worth, Kriz and Dominika came up with different expressions. rl Kriz: & 4x + 2y Dominika: & 2(2x+y) Who is correct?
The addition operation has some properties that allow to rewrite an algebraic expression without changing the values when evaluating. The first one has to do with the order of the addition.
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 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.Adding 0 to any number always results in the number itself.
Because of this, 0 is called the Additive Identity.
Dominika and her friends are playing the tabletop role playing game that they created.
Dominika's character needs to move very far as quickly as possible. It is good that she has upgrades to move faster! Her character can move 50 feet in one round, but she can roll a die to add additional distance. This additional distance can be written as d. 50+d In addition to this, Dominika has an upgrade item that adds 15 feet to the total distance. (50+d) + 15 Help Dominika do the following.
( 50+ d) + 15 ⇓ ( d+ 50)+15 Looking at the expression above, the next step would be to group the constant terms together. This can be done with the Associative Property of Addition. (d+50 )+15 ⇓ d+ (50+15 ) The final step is to complete the addition. d+( 50+15) ⇓ d+ 65 Doing this process, the expression has been rewritten as an expression with only two terms. The steps to get to this point can be summarized as follows.
| Step | Operation |
|---|---|
| First | Commutative Property of Addition |
| Second | Associative Property of Addition |
| Third | Evaluate the Addition |
d+65 When this expression is evaluated, the result is the same as evaluating the given original expression.
Similar to the Properties of Addition, the multiplication operation has some properties that allow to rewrite an algebraic expressions without modifying the results when evaluating.
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.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.Any number multiplied by 1 is equal to the number itself.
Because of this, the number 1 is called the Multiplicative Identity.
The result of multiplying any number by 0 is always 0.
As a consequence of this, if an entire expression is multiplied by 0, the result is 0. It does not matter the number of terms that the expression has. (a+29-3b+12* xy0.24)*0=0 endgathered
It has been shown that a*0=0. By the Commutative Property of Multiplication, 0* a is also equal to 0.
Dominika and Zain are preparing a cooperative attack to take down a strong enemy together.
z* 4/5 Another player gives Zain a boost that multiplies Zain's attack points by 54. ( z* 4/5 ) * 5/4 Write the expression for Zain's character's attack points as a single term with a coefficient.
1.2* (d* 1.5) Write this expression as a term with a single coefficient.
( z* 4/5 ) * 5/4 ⇓ z* (4/5 * 5/4) Now the fractions can be multiplied directly. Notice that the grouped fractions are reciprocals of one another. This means that multiplying them results in 1. z* (4/5 * 5/4) ⇓ z* 1 Finally, this expression can be simplified to z by using the Identity Property of Multiplication. z* 1 = z After the attack modifiers, Zain's character has their original attack points.
1.2* ( d* 1.5) ⇓ 1.2* ( 1.5 * d) Similar to Part A, the Associative Property of Multiplication can be used to group the constants. 1.2* (1.5 * d) ⇓ (1.2* 1.5) * d Finally, the product can be found. The expression can be written as a unique term with the variable d and its coefficient. ( 1.2* 1.5) * d = 1.8d Dominika's character has almost double their original attack power!
After a hard battle, Dominika and her friends went to buy some potions for health and magic.
They decided to buy x health potions and y magic potions. Dominika wrote an expression for the total amount of copper coins that they need to buy the potions. 5(2x + y) Every health potion has the same price and every magic potion has the same price.
Price ofxHealth Potions: price of a health potion* x Similarly, the price of y magic potions is the product of y and the price of one magic potion. Price ofyMagic Potions: price of a magic potion* y The total price of x health potions and y magic potions is the sum of these products. price of a health potion* x + price of a magic potion* y However, the given expression is written differently. 5(2x + y) The good thing is that the expression can be rewritten using the Distributive Property. This property shows how the multiplication of a number and a sum can be rewritten as a sum of products. a( b + c) = a b + a c A similar procedure can be performed on the given expression to rewrite it.
Now that the expression is rewritten, the x-term can be compared with the price of x health potions. price of a health potion* x ⇕ 10 x As previously stated, the total for the x health potions is the product of x by the price of a single health potion, which is of 10 copper.
10 x + 5 y This time the focus should be on the term with the variable y. This term can be compared with the price of y magic potions. price of a magic potion* y ⇕ 5 y This indicates the total price paid for the y magic potions, which is the result of multiplying y by the price of one magic potion, 5 copper.
In this lesson, different properties of operations were used to rewrite expressions into different expressions that evaluate to the same results. These expressions may be different, but they represent the same quantity and they are called equivalent expressions.
Two or more expressions are equivalent expressions if they have the same result when evaluated. In the case of numerical expressions, two equivalent expressions result in the same number when evaluating the operations. 12 - 6 &= 6 2*3 &= 6 Since both 12-6 and 2*3 equal 6, these expressions are equivalent. In a similar way, two algebraic expressions are equivalent if both expressions result in the same number for every value of the variables. r y + 4 2+y + 2 In both of these expressions, any value for y results in the same number. For example, substitute 5 for y.
ccc y + 4 & & 2+y+2 ⇓ & & ⇓ 5 + 4 = 9 & & 2+ 5+2=9With the loot from their quest, Dominika and her party go to a town to buy some useful equipment. The shop gives prices in copper coins.
Dominika wants to know the total that they need to buy the equipment, but she does not have a calculator nearby. Help Dominika to find the total using mental math.
Therefore, Dominika's party needs 130 copper coins to buy all three items.
Dominika and her party encountered a dragon!
However, instead of a battle, the dragon presented a quiz and asked for equivalent expressions of an algebraic expression. 14( 2z+1/7) Select all expressions that are equivalent to the expression above.
The given expression can be seen as the product of two numbers. One way to get an equivalent expression is to use the Commutative Property of Multiplication.
This means that this expression is equivalent to the given expression.
The Distributive Property can be used to compare this expression to the given expression. When simplified, both expressions should be equal to each other if they are equivalent. The given expression can be simplified by distributing 14.
Distribute 14
Multiply 14 by 2z
Multiply 14 by 1/7
a/b=.a /7./.b /7.
a/1=a
Now simplify the questionable expression by distributing 7.
Distribute 7
Identity Property of Multiplication
Multiply 7 by z/14
a/b=.a /7./.b /7.
This simplifed expression is different from the one given by the dragon. Therefore, these expressions are not equivalent.
Consider the simplification of the dragon's expression. 28z+2 This expression is different than the expression 2z+28, so these expressions are not equivalent.
Consider the simplification of the dragon's expression again. 28z+2 Applying the Commutative Property of Addition to this expression results in the next possible equivalent expression. 28z+2 = 2+28z The expressions are equivalent.
The previous expression was shown to be equivalent to the dragon's expression, so it can be compared to the final potential equivalent expression. 2+28z The constant term is a multiple of 2 and the coefficient of the variable term is also a multiple of 2. Knowing this, both terms can be rewritten. 2*1+2*14z The 2 can be separated from both terms by using the Distributive Property. 2*1+2*14z = 2(1+14z) The expression is equivalent to the previous expression, so it is also equivalent to the expression given by the dragon!
At the beginning of this lesson, it was mentioned that in the game there are three different types of coins with different values.
The copper coins are the least valuable. The gold coins are worth 4 copper coins and the silver coins are worth 2 copper coins. Wondering how many copper coins x gold coins and y silver coins are worth, Dominika and Kriz proposed two different expressions. rl Kriz: & 4x + 2y Dominika: & 2(2x+y) The total copper coins can be found by adding the copper coins that correspond to x gold coins to the copper coins from the y silver coins. The corresponding copper coins from x gold coins are the result of multiplying the number of gold coins x by the number of copper coins that one gold coin is worth, 4. rl Gold Coins: & 4x In a similar way, the number of copper coins equivalent to y silver coins is the product of 2 and y. rl Gold Coins: & 4x Silver Coins: & 2y The total copper coins from both types of coins is the sum of these expressions. 4x + 2y This means that Kriz is right. This is great, but there is something important to note. Both coefficients of the expression can be rewritten as multiples of 2. This factor can then be separated from the addition by using the Distributive Property.
Rewrite 4x as 2*2x
Rewrite 2y as 2*1y
Factor out 2
Identity Property of Multiplication
Which of the following expressions is equivalent to 4+x+4? A.& x * 4 B.& x(4* x) C.& x+ 4 +4 D.& (4+x)+x
Consider the given options that might be an equivalent expression for 4+x+4. A.& x * 4 B.& x(4* x) C.& x+ 4 +4 D.& (4+x)+x We want to know which of these is equivalent to the given expression. Equivalent expressions are equal no matter what number is substituted for the same variable. With this in mind, we can evaluate each option for a value of the variable and see if they are equal. Let's start by evaluating the given expression for x= 1.
The value of the given expression is 9. We can do the same for the given options to see which of them is an equivalent expression for x= 1. Let's see the results in a table!
| Expression | Substitution | Value | Equivalent Expression? |
|---|---|---|---|
| x * 4 | 1* 4 | 4 | No |
| x (4* x) | 1(4* 1) | 4 | No |
| x +4+4 | 1+4+4 | 9 | Yes |
| (4+x)+x | (4+ 1)+ 1 | 6 | No |
As we can see, only x+4+4 has the same value as the given expression. This means that this expression might be equivalent! To make sure that the expression is indeed equivalent, let's see if there are any properties that we can apply to modify the given expression to get the expression in C. Let's compare them first! Given Expression:& 4+x+4 Expression C:& x+4 +4 The terms in these expressions are the same but the order is different. The good thing is that we can reorder the given expression by using the Commutative Property of Addition to get expression C. 4+x+4 = x+4+4 This means that the correct answer is C.
A property is being demonstrated. 5* (y* 9) = (5* y) * 9 Which property is it?
We want to identify the operation being performed to identify which of the Properties of Operations is being demonstrated. 5* (y* 9) = (5* y) * 9 In this case, the terms are being multiplied. The property being used shows that changing the grouping of the factors being multiplied does not change the product. This relates to the Associative Property of Multiplication.
In this exercise, we saw an example of the Associative Property of Multiplication. Now, let's review some other Properties of Operations.
Simplify the following expression. 10+(14+a)
We need to examine the given expression to simplify it. First, let's look at the operations used in the expression. 10+(14+a) The expression only has additions. According to the order of operations, a constant should be added to a variable first. However, we cannot complete this operation. Instead, let's simplify the expression by adding the two constants. We can use the Associative Property of Addition to group the constants. 10+(14+a) = (10+14)+a Now we can add the constants.
Note that we can also use the Commutative Property of Addition to have the variable term before the constant term. a+24=24+a Since we cannot add the variable and the constant, we have simplified the expression. Good job!
Simplify the following expression. 7(n+2)
We want to find an equivalent expression with the least number of terms to simplify the given expression. Consider the given expression. 7(n+2) We can see it as the product of two factors. Let's use the Distributive Property to find an equivalent expression. 7(n+2)&=7(n)+7(2) &=7n+14 The variables and constants cannot be added without evaluating the variable. Because of this, the expression is simplified. We did it!
Consider the following expression. 4(3a+2) Which of the following is an equivalent expression? Select all that apply.
We are asked to determine which of the given expressions are equivalent to the expression 4(3a+2).
| Expression | Is It Equivalent to 4(3a+2)? |
|---|---|
| 12a+8 | |
| 6a+8+6a | |
| 12a+6 |
Two expressions are equivalent if one expression can be rewritten into the other one by using Properties of Operations. First, let's try to rewrite the expression 4(3a+2) using the Distributive Property.
We found that 4(3a+2) and 12a+8 are equivalent expressions. This is one of our options!
| Expression | Is It Equivalent to 4(3a+2)? |
|---|---|
| 12a+8 | Yes |
| 6a+8+6a | |
| 12a+6 |
Now let's use the Properties of Operations to rewrite the next expression.
We can see that 6a+8+6a and 12a+8 are equivalent expressions. Therefore, the expression is also equivalent to 4(3a+2)!
| Expression | Is It Equivalent to 4(3a+2)? |
|---|---|
| 12a+8 | Yes |
| 6a+8+6a | Yes |
| 12a+6 |
Now let's determine if the last expression is equivalent to the others. Earlier, we found that 4(3a+2) is equivalent to 12a+8. 4(3a+2)=12a+8 Notice that the expression 12a+8 is not equivalent to 12a+6 because we cannot turn 8 into 6 using the Properties of Operations. 12a+8 ≠ 12a+6 ⇕ 4(3a+2) ≠ 12a+6 This means that 4(3a+2) is not equivalent to 12a+6.
| Expression | Is It Equivalent to 4(3a+2)? |
|---|---|
| 12a+8 | Yes |
| 6a+8+6a | Yes |
| 12a+6 | No |
Now we know which expressions are equivalent. Great job!