Evaluating expressions (article) | Khan Academy (2024)

Learn to evaluate all sorts of expressions: expressions with one variable, two variables, fractions and decimals, and even expressions in word problems.

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Ana Chavarria
8 years agoPosted 8 years ago. Direct link to Ana Chavarria's post “Cam has 32 dollars. How m...”
Cam has 32 dollars. How many roses can he afford to buy?
Assume that he wants to buy as many roses as he can.
how do you solve this and come out with the answer 6. Can you please explain?
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(10 votes)
- StarryNight
  8 years agoPosted 8 years ago. Direct link to StarryNight's post “The expression 2+5r equal...”
  The expression 2+5r equals the cost of the roses, which is 36. So you can replace "cost of roses" with 36 and get the expression 2+5r=36. Now you have an equation that you have to solve. Solving this algebraically requires knowledge of algebra higher than what you've got now, so try using the guess-and-check method. Make a chart of amounts of roses and the price that each one of them would cost. 2 roses cost 12 dollars, 3 roses cost 17 dollars, 4 roses cost 22 dollars, 5 roses cost 27 dollars, and 6 roses cost 32 dollars. And that's your answer!
  If you want to find out how to solve the equation algebraically, head over to these videos: https://www.khanacademy.org/math/algebra-home/alg-basic-eq-ineq
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  (1 vote)
Darpan Rastogi
8 years agoPosted 8 years ago. Direct link to Darpan Rastogi's post “What is PEMDAS? Why do we...”
What is PEMDAS? Why do we have to follow it?
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(5 votes)
- cheese33
  See Also
  7.1: Simplifying Rational Expressions Intro to rational expressions (article) | Khan Academy Multiplying rational expressions (article) | Khan Academy
  8 years agoPosted 8 years ago. Direct link to cheese33's post “Good question! PEMDAS is...”
  Good question!
  PEMDAS is an acronym for:
  P – Parentheses
  E – Exponents
  M – Multiplication
  D –Division
  A –Addition
  S –Subtraction
  Note that you do M and D at the same time, and A and S at the same time. When you have a complicated expression, this is the order of which you solve the operations.
  For example, let's take the expression:
  5 - 2 * 8^2 + (5 - 3 / 3)
  
  Now, if you were to do it left to right, you would do:
  3 * 8 ^ 2 + (5 - 3 / 3)
  24 ^ 2 + (5 - 3 / 3)
  576 + (5 - 3 / 3)
  581 - 3 / 3
  578 / 3
  192.66666667
  But, if you use PEMDAS, you get:
  5 - 2 * 8^2 + (5 - 3 / 3) //1st: Parentheses 5 - 2 * 8^2 + (5 - 1) //Division is done first 5 - 2 * 8^2 + 4 //2nd: Exponents 5 - 2 * 64 + 4 //3rd: Multiplication 5 - 128 + 4 //4th: Addition/Subtraction -123 + 4 -119 //Answer!
  
  So why do we use PEMDAS? Well, without it, there would be no guidelines on what to do first.
  Learn more here: http://study.com/academy/lesson/what-is-pemdas-definition-rule-examples.html
  Comment on cheese33's post “Good question! PEMDAS is...”
  (7 votes)
ojinkins
8 years agoPosted 8 years ago. Direct link to ojinkins's post “I don't want to go to a f...”
I don't want to go to a flower store where I can get charged 2$ for buying 0 roses.
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(6 votes)
- ethan.kuo
  5 months agoPosted 5 months ago. Direct link to ethan.kuo's post “Well, maybe you can buy i...”
  Well, maybe you can buy infinite number of flowers and get the most out of that $2.
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  (1 vote)
Md. Durjoy Mia
7 months agoPosted 7 months ago. Direct link to Md. Durjoy Mia's post “the value of the constant...”
the value of the constant is the same regardless of the number of roses.
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(3 votes)
Mehboob Rehan
8 years agoPosted 8 years ago. Direct link to Mehboob Rehan's post “I saw a question about PE...”
I saw a question about PEMDAS and Its very good explanation, What is BOADMASS and when is that used?
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(2 votes)
- Kim Seidel
  8 years agoPosted 8 years ago. Direct link to Kim Seidel's post “It is spelled: BODMAS. ...”
  It is spelled: BODMAS. It is exactly the same as PEMDAS. There are also BEDMAS and BIDMAS. They just use different words to represent the same exact rules for order of operations.
  B = Brackets or P = Parentheses
  O = Orders, or E = Exponents; or I = Indices.
  MD = Multiplication & Division; or DM = Division & Multiplicaton
  AS = Addition & Subtraction
  Here are some examples of where these are used according to Wikipedia: PEMDAS is used in the US. BODMAS is used in the UK & Australia. BEDMAS is used in Canada & New Zealand. BIDMAS is used in some African countries.
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  (2 votes)
nurali
8 years agoPosted 8 years ago. Direct link to nurali's post “I don't understand the wo...”
I don't understand the word problem with muffins and cakes
can someone explain it.
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(2 votes)
- Math Enjoyer
  a year agoPosted a year ago. Direct link to Math Enjoyer's post “In the question it asks u...”
  In the question it asks us to solve, "how much money do you get from selling 3 muffins and 4 cakes,"and it tells us that the price of muffins is 2$, and the cakes are 10$.So now the equation is 2 times 3 + 10 times 4. First we multiply which then gives us 6+40 with will give us 46$
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  (1 vote)
Aaryan Paul
8 years agoPosted 8 years ago. Direct link to Aaryan Paul's post “How many dollars in one p...”
How many dollars in one pound?
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(0 votes)
- Kim Seidel
  8 years agoPosted 8 years ago. Direct link to Kim Seidel's post “Currency exchange rates v...”
  Currency exchange rates vary daily. You would need to look it up on the internet for the current exchange rate.
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  (4 votes)
Aubrey Carr
8 years agoPosted 8 years ago. Direct link to Aubrey Carr's post “On the 8th problem from t...”
On the 8th problem from the top, I cannot seem to get the answer right.
The problem is 3/2y-3+5/3z y=4 z=3. I converted the fractions to decimals before multiplying them, and I keep coming up with 10.8. I know I'm probably doing something stupidly wrong, but can you please tell me what?
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(2 votes)
- Kim Seidel
  8 years agoPosted 8 years ago. Direct link to Kim Seidel's post “The error is from convert...”
  The error is from converting the fractions to decimals. 5/3 is a repeating decimal (1.666...). You likely changed it into 1.6 or 1.7. Neither one is equal to 5/3. Unless the fraction creates a terminating decimal, you are better off using the fraction to maintain its entire value. By rounding / truncating repeating decimals, you no longer have the same value and you get incorrect answers when exact answers are needed.
  3/2 (4/1) + 5/3 (3/1)
  Cancel common factors
  3/1 (2/1) + 5/1 (1/1)
  Multiply, then add
  6 + 5 = 11
  Hope this helps.
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  (0 votes)
Sree Chaitanya. B
8 years agoPosted 8 years ago. Direct link to Sree Chaitanya. B's post “If he wants to cut the mo...”
If he wants to cut the money and then if the cost of a tulip is 1 dollar dollar then how if you have to spend only $31 then how much money should he pay
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(0 votes)
prince_eg17
8 years agoPosted 8 years ago. Direct link to prince_eg17's post “it is not the double cost...”
it is not the double cost of three roses because it builds up a different price
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(0 votes)

Evaluating expressions (article) | Khan Academy (2024)

FAQs

How do you evaluate an expression answer? ›

The order of operations should always be used to evaluate the expression. For any given expression, this means solving within the parentheses, then the exponents, then multiplying or dividing from left to right, and finally adding or subtracting left to right. Not following this order will give the incorrect answer.

How to solve evaluating expressions step by step? ›

Steps to Evaluate and Simplify Algebraic Expressions

Step 1: Obtain the value of variables involved in the expression.
Step 2: Substitute the numerical value for each variable wherever they appear in the expression.
Step 3: Simplify the arithmetic expression obtained by using the rules of the order of operations.

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Mar 26, 2024

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What is the best way to evaluate an expression? ›

To evaluate an algebraic expression, you have to substitute a number for each variable and perform the arithmetic operations. In the example above, the variable x is equal to 6 since 6 + 6 = 12. If we know the value of our variables, we can replace the variables with their values and then evaluate the expression.

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How do you evaluate an expression with multiple variables? ›

Evaluating expressions with multiple variables involves substituting given values for each variable and simplifying the expression. By replacing variables with their corresponding values, we can easily compute the result of expressions, even for more complex examples with multiple terms and operations.

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How do you write an evaluate answer? ›

Evaluate questions refer to the end of the process and require you to look back on the effectiveness of something. When answering evaluate questions, you need to: make a judgement. support this judgement with evidence that shows why you said it was effective or ineffective.

How to evaluate expressions in 7th grade? ›

An expression can combine arithmetic operations with numbers, letters, or both. Letters are used to represent variables. To evaluate an expression, find the value of the expression by replacing each variable in the expression with a given number.

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What is the first step for evaluating this expression? ›

The first step in evaluating an expression is to identify what the given values are for each variable, and then substitute those values into the expression for the variables.

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In what order do you evaluate expressions? ›

PE(MD)(AS) is a mnemonic device to remember the order of operations. This means that the order is: Parentheses, Exponents (this will be incorporated later), Multiplication and Division (taken together from left to right), and finally, Addition and Subtraction (taken together from left to right).

How do you evaluate a question answer? ›

When answering an evaluate question, you should give a short description of the strategy or project being evaluated, before giving a conclusion. The conclusion should be backed-up by evidence to support it.

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How do you evaluate a function answer? ›

Evaluating a function means to substitute a variable with its given number or expression. Given f(x) = 2x + 4, evaluate f(5). This question asks you to substitute 5 for x and simplify. To add functions, add their outputs; to subtract functions, subtract their outputs.

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How do you write an evaluate response? ›

Evaluative writing has three key elements: judgment, criteria, and evidence. The judgment is the writer's opinion on the topic. The criteria are the reasons for the writer's judgment. The evidence is proof or information that provides support for the criteria.