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Algebra 1
Course: Algebra 1 > Unit 1
Lesson 3: Substitution and evaluating expressions- Evaluating expressions with two variables
- Evaluating expressions with two variables
- Evaluating expressions with multiple variables
- Evaluating expressions with two variables: fractions & decimals
- Evaluating expressions with two variables: fractions & decimals
- Evaluating expressions with multiple variables: fractions & decimals
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Evaluating expressions with two variables: fractions & decimals
We've already evaluated expressions with two variables. Now it's time to do it with fractions and decimals.
Let's study another example.
Evaluate start fraction, 1, divided by, 3, end fraction, a, minus, 1, minus, start fraction, 1, divided by, 2, end fraction, b when a, equals, 12 and b, equals, 6.
Now, let's practice
Want to join the conversation?
- I really don't understand problem 1, could someone explain??
Why isn't it 0?(13 votes)- I'm going to assume you mean problem 1 in "let's practice" rather than the 1st problem in the video or just below the video.
Problem 1 in practice is: (3/2)y-3+(5/3)z given the values of y=4 and z=3
Substitute the vales for the variables:
(3/2)(4/1)-3+(5/3)(3/1)
Follow PEMDAS rules. Multiply first.
(3/2)(4/1)=12/2=6
(5/3)(3/1)=15/3=5
So, the expression is now: 6-3+5
Now, add and subtract from left to right.
6-3+5 = 3+5 = 8
The answer is 8. Why do you think it should be 0?
Hope this helps.(75 votes)
- Why is the answer to the second question 11? If I follow the order of operations shouldn't the answer be 5? Do addition first.. so 5 + 3 = 8.. then subtraction 13 - 8 = 5..(7 votes)
- You aren't quite following order of operations. In PEMDAS, there are 4 steps, not 6.
P = Parentheses: Do any work inside first
E = Exponents: Do any exponents or radicals next
MD = Multiply & Divide: These are one step. You need to work them from left to right
AS = Add & Subtract: These are one step. Again, you need to work them from left to right
So, when applied to the 2nd problem: 13-5+3
You go left to right: 13-5=8
Then 8+3=11
Hope this helps.(58 votes)
- You guys really help people out when you help them with the problems.
Good job!(14 votes) - Wait, so, the first practice question has 3 over 2, isn't that an improper fraction? Am I supposed to treat it as an improper fraction and divide 3 into 2? Or, do I treat it as a normal fraction and try and figure out the problem? When I try to divide 3 into 2, i get 0.666... and so on. Thanks!(6 votes)
- It's good that you saw that the answer 0.666... does not make good sense for the improper fraction 3 over 2. This should tell you that dividing 3 into 2 is an incorrect method.
The fraction 3 over 2 actually means dividing 2 into 3. You should get 1.5 for the fraction 3 over 2.
In general, the fraction a over b means dividing b into a, or equivalently dividing a by b.
Have a blessed, wonderful day!(7 votes)
- can somebody help me Evaluate 3/2 y - 3 +5/3 z when y=4 and z=3 like im just lost(6 votes)
- 3/2y-3+5/3z y=4 z=3
3/2*4/1-3+5/3*3/1
12/2-3+15/3
6-3+5=8
||I was thinking it is solved this way||(1 vote)
- I am a bit stuck. how do we do 3/2 • 4 and 5/3 • 3
? Please help!(4 votes)- Several ways to do it, 3/2*4/1=3*4/2=12/2=6 or 3*4/2=3*2=6.(7 votes)
- How does one divide when one has 4(.5)(4 votes)
- I'm not quite sure I understand your question. Can you please rephrase it?(5 votes)
- on the last step why was he able to eliminate posative 3 and negative 3? so quick without going through pemdas i know it will come out to 8 either way but did you use a faster way to get the answer? = 3 + 8 - 3(5 votes)
- It's a faster way: 3 + 8 + (-3). Commutative Property:
3 + (-3) + 8. 3-3 = 0. 0 + 8 = 8.
Or you can just mental math it and cancel out the 3 without rearranging the equation.(4 votes)
- I dont understand problem 2. To be more specific I dont understand the fraction part 6(1/2). Could someone please help me.(5 votes)
- Hey! To put it simply you just have to divide 6 by 2 to cut it in half in 13 - 0.5w + 6x when w =10 and x = 1/2. That makes the expression 13 - 5 + 3 = 11 if you follow PEMDAS.
Hope this helps! ^o^(4 votes)
- the answer. i need it. It won't let me type in fraction(4 votes)
- When typing fractions onto spaces when inputting answers's questions, try using the "slash" symbol, /,or the fraction command inside the pop-out menu.(6 votes)