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## Algebra (all content)

### Course: Algebra (all content)>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.
• 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.
• Can someone help me? The video didn't help me and i am struggling.
• What do you need help with?
• 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 :)
• As a graduating senior I thank you for reminding me of such a useful tip lol
• 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.
• why do you have to make 0.25 a fraction?
• You don't. 8(0.25) = 2, so you get the same result in decimal form.
• How did 7x0.5=3.5?
How did 8x0.25=2?
• Seems like you to need to review the lessons for multiplying with decimal numbers.
7x0.5 = 3.5 because 7x5=35 and the answer needs 1 decimal place given that there is one decimal place in the original number.

0.7x0.5 = 0.35 because now the original 2 numbers have 2 decimal places in total. So, the answer requires 2 decimal places.

8x0.25 = 2 because 8x25 = 200 and the result needs 2 decimal places due to the 2 decimal places in the original numbers. This change the 200 into 2.00 or just 2.

• I don't really get it and i watched this video 3 times already... :/
(1 vote)
• Can you explain how you got the answer? How do you caculate 0.25(also 1/4) multiply 12? The 12(1/4)
• You multiply 0.25 or 1/4 or 25/100 times 12 and that = 3.