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### Course: Integrated math 1>Unit 1

Lesson 3: Substitution and evaluating expressions

# Evaluating expressions with two variables: fractions & decimals

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.

## Want to join the conversation?

• at 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.
• 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!
• 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.
• 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.
• Can someone help me? The video didn't help me and i am struggling.
• 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.
(1 vote)
• 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.
• PEMDAS or GEMDAS always applies whenever you do something like this, right? I hope I'm right.
• Yes, the order of operations rules always apply in problems like these.
• When we say decimals isn't the decimals said as for example 0.45 said as 0 and 45 hundredths?
• You can say it that way. Or, you can just say: 45 hundredths.
(1 vote)
• at in the video he says if we get half of 7 we get 3.5 but how does he get the that?