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### Course: Algebra 1>Unit 3

Lesson 2: Appropriate units

# Formulas and units: Comparing rates

When using formulas to calculate real-world quantities, we need to make sure our units are consistent. In this video, one growth rate is given in centimeters per week and the other is given in millimeters per day. In order to compare which rate is faster, we need to convert one of the rates to units that match the other rate.

## Want to join the conversation?

• ok is everybody watching a different video or am i missing something? because all see him talking about is the plant growth.
• He is actually talking about how to convert between units. The plant growth is just an example
• The videos all make sense, but the practice questions that I've gotten so far go completely over my head when asking about converting formulas of newtons and joules. You can say it's all the same but it is very confusing how the two apply by saying one number is itself a formula and somehow ask me to convert that formula to another formula?

Why would you give lessons with simple conversions and then start throwing random things into the practice?

This isn't helping me learn, all it is doing is frustrating and confusing me. Leave the physics questions for the physics course and help me understand the basics of Algebra 1 in a clear and direct way.
• This is very well said. I've had to seek out other resources to help me learn the extra material in the practices and the questions are completely different from what's being taught in the videos. Khan academy needs to really review the curriculum.
• So in this case, Y stands for yield, C stands for carrots, and P stands for plants?
• my plant grows less then a millimeter per week.. (i measured it)
• Yes most plants grow slowly
• I was asked a question that included formulas in physics in the 'Formula & units' excercise, when I have never touched physics, they are units that not only describe something like a newton, a joule, or whatever, they're also using thing like time^2, which is not familiar with me.
• can someone help me with one of the problems related to this vid. It is about Formulas and Units practice. The question about "what calculation will give us the sum of the forces that act on the object, in Newtons." I was really confused by the weird wording and don't know what to do.
• Simpler method,write the rates like this:
2cm/week 3mm/day multiply the second rate by 7
then we get 21mm/week.We know that 10mm is equal to
1cm with that knowledge we rewrite the 2cm as 20mm
then we see that Martine's plant grows faster.

If anyone sees an error in my methods please tell me
and describe the error.
• Took me 5 seconds. Skip forward and he somehow finds the most complicated way on answering the question.
• why the answer is `C/P` if we have `2C/P`, but the answer is `C^2/P` if we have `C^2/P` ?

I mean we are multiplying the number in situations, why do we write what are we multiplying by when we multiply buy the number/variable itself, but not when we multiply by other number ?