okay just in case anyone (like me on several occasions) has forgotten, here's a quick way to multiply numbers with decimals: - 1. ignore the decimal point and turn it into a regular number - 2. multiply that with the other number - 3. count how many numbers are behind the decimal point - 4. move the decimal point across in your answer that many digits - 5. boom, there's the answer e.g. 9 x 4.5 - 1. 4.5 to 45 - 2. 9 x 45 = 405 - 3. there is 1 number behind the decimal point in 4.5 - 4. 405 becomes 40.5 - 5. the answer is 40.5 there. to whoever finds this useful, you're welcome :)

I have a more efficient way. 9 x 4.5 10 x 4.5 - 4.5 45 - 4.5 40.5 Boom!

at 1:03 in the video he says if we get half of 7 we get 3.5 but how does he get the that?

The decimal representation of 1/2 is 0.5, which is what he uses in the video. He wrote 0.5 and says "one half", since they a representations of the same thing. Hope that helped.

Why does Sal halve 7 when he multiplies it by 0.5?

because if you multiply anything by any value less than 1, it gets necessarily cut in half.

PEMDAS or GEMDAS always applies whenever you do something like this, right? I hope I'm right. 1:48

Yes, the order of operations rules always apply in problems like these.

i dont understand how 12 (1/4) equals 3 can someone help

12 in fraction form is 12/1 Multiply 12/1 (1/4) = (12*1)/(1*4) = 12/4 = 3 Hope this helps.

How does this type of pb solving resolve real world dilemmas??

There are many formulas used in the real world, perimeter, area, compounded interest, tax calculations, etc. Formulas use variables. If you want to use the formula, you need to know how to replace the variables with the appropriate values and do the math. The values given to the variables could be decimals, fractions, mixed numbers, etc. The formula could have a fraction or a decimal.

at 1:03 in the video he says if we get half of 7 we get 3.5 but how does he get the that?

you multiply 7 and 0.5 that would give you 3.5 when a number is but into a decimal like 0.5 for example it become half of the number when multiplying just like 12 times 0.5 it become 6

Why is he dividing instead of multiplying the numbers by the ones in parentheses??

When you are multiplying a whole number by a fraction it is the same thing as dividing the answer. For example 36 times 1/6, here it the same thing as 36/6 =6 Hope this helps :)

Main content

Algebra 1

Course: Algebra 1 > Unit 1

Lesson 3: Substitution and evaluating expressions

Evaluating expressions with two variables: fractions & decimals

Name: Evaluating expressions with two variables: fractions & decimals
Uploaded: 2015-06-03T17:47:55Z
Description: Evaluating expressions with two variables involves substituting the given values for each variable and simplifying the expression. By practicing with examples, we can improve our skills in solving these types of problems, ultimately enhancing our understanding of algebraic expressions and their real-world applications.

Google Classroom

Evaluating expressions with two variables involves substituting the given values for each variable and simplifying the expression. By practicing with examples, we can improve our skills in solving these types of problems, ultimately enhancing our understanding of algebraic expressions and their real-world applications.

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RKrause100
Posted 8 years ago. Direct link to RKrause100's post “at 1:03 in the video he s...”
at
1:03
in the video he says if we get half of 7 we get 3.5 but how does he get the that?
Button navigates to signup pageComment on RKrause100's post “at 1:03 in the video he s...”
(25 votes)
Answer
- Stefen
  Posted 8 years ago. Direct link to Stefen's post “The decimal representatio...”
  The decimal representation of 1/2 is 0.5, which is what he uses in the video.
  He wrote 0.5 and says "one half", since they a representations of the same thing.
  Hope that helped.
  Comment on Stefen's post “The decimal representatio...”
  (38 votes)
Kaze Haibara 📴
Posted 7 months ago. Direct link to Kaze Haibara 📴's post “okay just in case anyone ...”
okay just in case anyone (like me on several occasions) has forgotten, here's a quick way to multiply numbers with decimals:

- 1. ignore the decimal point and turn it into a regular number
- 2. multiply that with the other number
- 3. count how many numbers are behind the decimal point
- 4. move the decimal point across in your answer that many digits
- 5. boom, there's the answer

e.g. 9 x 4.5
- 1. 4.5 to 45
- 2. 9 x 45 = 405
- 3. there is 1 number behind the decimal point in 4.5
- 4. 405 becomes 40.5
- 5. the answer is 40.5

there.
to whoever finds this useful, you're welcome :)
Button navigates to signup pageButton navigates to signup page
(27 votes)
Answer
- Jay :)
  Posted 6 months ago. Direct link to Jay :)'s post “I have a more efficient w...”
  I have a more efficient way.
  9 x 4.5
  10 x 4.5 - 4.5
  45 - 4.5
  40.5
  Boom!
  Comment on Jay :)'s post “I have a more efficient w...”
  (2 votes)
Quinn
Posted 4 years ago. Direct link to Quinn's post “Why does Sal halve 7 when...”
Why does Sal halve 7 when he multiplies it by 0.5?
Button navigates to signup pageComment on Quinn's post “Why does Sal halve 7 when...”
(6 votes)
Answer
- 24hAgardi
  Posted 3 years ago. Direct link to 24hAgardi's post “because if you multiply a...”
  because if you multiply anything by any value less than 1, it gets necessarily cut in half.
  Comment on 24hAgardi's post “because if you multiply a...”
  (11 votes)
Ijaz Durrani
Posted 6 months ago. Direct link to Ijaz Durrani's post “How does this type of pb ...”
How does this type of pb solving resolve real world dilemmas??
Button navigates to signup pageComment on Ijaz Durrani's post “How does this type of pb ...”
(4 votes)
Answer
- Kim Seidel
  Posted 6 months ago. Direct link to Kim Seidel's post “There are many formulas u...”
  There are many formulas used in the real world, perimeter, area, compounded interest, tax calculations, etc. Formulas use variables. If you want to use the formula, you need to know how to replace the variables with the appropriate values and do the math. The values given to the variables could be decimals, fractions, mixed numbers, etc. The formula could have a fraction or a decimal.
  Button navigates to signup page
  (13 votes)
Cam'Ron Welcome
Posted 5 years ago. Direct link to Cam'Ron Welcome's post “Can someone help me? The ...”
Can someone help me? The video didn't help me and i am struggling.
Button navigates to signup pageComment on Cam'Ron Welcome's post “Can someone help me? The ...”
(8 votes)
Answer
- Ashaz Moen
  Posted 3 years ago. Direct link to Ashaz Moen's post “First: Take a few steps b...”
  First: Take a few steps back.
  Second: The variables are ever changing values, and here the variables are less than 1. You can try learning what the decimal values for fractions are, and that can be easier to multiply by as 1/2 times 7. Or you can directly multiply o.5 times 7.
  Button navigates to signup page
  (1 vote)
Film Yang
Posted 10 months ago. Direct link to Film Yang's post “i dont understand how 12 ...”
i dont understand how 12 (1/4) equals 3 can someone help
Button navigates to signup pageComment on Film Yang's post “i dont understand how 12 ...”
(5 votes)
Answer
- Kim Seidel
  Posted 10 months ago. Direct link to Kim Seidel's post “12 in fraction form is 12...”
  12 in fraction form is 12/1
  Multiply 12/1 (1/4) = (12*1)/(1*4) = 12/4 = 3
  Hope this helps.
  Comment on Kim Seidel's post “12 in fraction form is 12...”
  (6 votes)
OrderPhoenixCAPT
Posted 4 months ago. Direct link to OrderPhoenixCAPT's post “PEMDAS or GEMDAS always a...”
PEMDAS or GEMDAS always applies whenever you do something like this, right? I hope I'm right.
1:48
Button navigates to signup pageComment on OrderPhoenixCAPT's post “PEMDAS or GEMDAS always a...”
(6 votes)
Answer
- Kim Seidel
  Posted 4 months ago. Direct link to Kim Seidel's post “Yes, the order of operati...”
  Yes, the order of operations rules always apply in problems like these.
  Button navigates to signup page
  (2 votes)
Sammie
Posted 7 years ago. Direct link to Sammie's post “When we say decimals isn'...”
When we say decimals isn't the decimals said as for example 0.45 said as 0 and 45 hundredths?
Button navigates to signup pageButton navigates to signup page
(5 votes)
Answer
- Kim Seidel
  Posted 7 years ago. Direct link to Kim Seidel's post “You can say it that way. ...”
  You can say it that way. Or, you can just say: 45 hundredths.
  Comment on Kim Seidel's post “You can say it that way. ...”
  (1 vote)
Flame Hawk
Posted 7 months ago. Direct link to Flame Hawk's post “at 1:03 in the video he ...”
at
1:03
in the video he says if we get half of 7 we get 3.5 but how does he get the that?
Button navigates to signup pageComment on Flame Hawk's post “at 1:03 in the video he ...”
(4 votes)
Answer
- e.apau646
  Posted 6 months ago. Direct link to e.apau646's post “you multiply 7 and 0.5 th...”
  you multiply 7 and 0.5 that would give you 3.5 when a number is but into a decimal like 0.5 for example it become half of the number when multiplying just like 12 times 0.5 it become 6
  Button navigates to signup page
  (2 votes)
Allie0143
Posted 4 months ago. Direct link to Allie0143's post “Why is he dividing instea...”
Why is he dividing instead of multiplying the numbers by the ones in parentheses??
Button navigates to signup pageButton navigates to signup page
(1 vote)
Answer
- Poonam.Renu
  Posted 4 months ago. Direct link to Poonam.Renu's post “When you are multiplying ...”
  When you are multiplying a whole number by a fraction it is the same thing as dividing the answer. For example 36 times 1/6, here it the same thing as 36/6 =6
  
  Hope this helps :)
  Button navigates to signup page
  (4 votes)

Video transcript

- [Voiceover] Let's see if we can give ourselves some practice evaluating expressions that have two different variables in them So let's see if we can evaluate the expression seven J plus five minus eight K, when J is equal to 0.5 and K is equal to 0.25. So why don't you try to pause the video and evaluate this first before we work through it together. Alright, so if we want to evaluate this thing, everywhere we see a J we want to replace it with a 0.5 and everywhere we see a K we want to replace it with a 0.25, so let's do that. This is going to be seven times, and instead of J I'm gonna put a zero, a 0.5 in there. And then we have plus five minus eight times K. And K we're saying is 0.25. 0.25. So what is this going to be equal to? So if I were to take, if I were to take, and I can color code this, seven times 0.5. Half of 7, that's going to be three and a half, 3.5. Then I have plus five. And then I'm gonna subtract. I am subtracting eight times 0.25. 0.25, this is 1/4. I could rewrite this if I want. 0.25, that's the same thing as 1/4. Eight times 1/4, or another way to think about it is eight divided by four is gonna be equal to two. So this whole thing over here is going to be equal to two. So it's gonna be minus, we have this minus out here, so minus two. And what is this going to be? Well, let's think about it. 3.5 plus five is 8.5, minus two is going to be 6.5. So this is equal to this, is equal to 6.5. Let's do another one of these. Alright. And we'll, just like before, try to work through it on your own before we do it together. Alright, now let's do it together. So over here I have this expression 0.1 M plus eight minus 12 N, when M is equal to 30 and N is equal to 1/4. Alright. So everywhere I see an M I want to replace with a 30. And everywhere I see an N I want to replace with a 1/4. So this is going to be equal to 0.1 times M. M is 30. Times 30 plus eight minus 12 times N, where N is 1/4. N is 1/4. So what is, what is 1/10, This right over here, 0.1, that's the same thing as 1/10 of 30? Well 1/10 of 30, that's going to be three. So this part is three. And we have three plus eight. And then we're gonna have minus. Well what is 12 times 1/4? That's gonna be 12/4, or 12 divided by four, which is going to be equal to three. And now when we evaluate this, so that is equal to this, we have three plus eight minus three. Well, threes are going to, you know positive three, then you're gonna subtract three, and you're just going to be left with, you're just going to be left with an eight. And you're done. This expression when M is equal to 30 and N is equal to 1/4 is equal to eight.