September 28, 2020, 06:06:20 PM
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### Topic: Dimensional Analysis  (Read 143 times)

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#### loserthelissa

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##### Dimensional Analysis
« on: September 15, 2020, 03:29:45 PM »
So, I definitely failed a quiz today. We had this question:
You are discussing marriage with your significant other and decide to find out how much a ring would cost. You go to a jeweler and choose a model ring you like that is made out of plastic. The plastic ring weighs 3.5632 g and the plastic has a density of 1.21 g/mL. How much would the gold for the same ring cost? (The density of gold is 19.3 g/cm3, the price of gold is  \$1972/troy oz, and there are 31.105 grams per troy oz.)

I got the wrong answer, I believe it was 3600 if I read the answer key right. I was wondering how you could do this? I did it twice and got around 230 and 14 both times and I knew they were wrong but I could not figure it out. Any help would be appreciated. I believe I messed up on the density part? If it was the density, I have no idea how to do it that is why I didn't really.
« Last Edit: September 15, 2020, 03:33:09 PM by Borek »

#### mjc123

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##### Re: Dimensional Analysis
« Reply #1 on: September 15, 2020, 04:32:05 PM »
You have multiplied by 1.21/19.3 when you should have multiplied by 19.3/1.21. Do you understand why? (It might help, when writing out your units, to write "g gold" or "g plastic" rather than just "g".)

#### loserthelissa

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##### Re: Dimensional Analysis
« Reply #2 on: September 15, 2020, 04:44:01 PM »
You have multiplied by 1.21/19.3 when you should have multiplied by 19.3/1.21. Do you understand why? (It might help, when writing out your units, to write "g gold" or "g plastic" rather than just "g".)
Dang, okay, I was wondering about that. I guess I did not really think to do 19.3/1.21. I do not really understand why but I did have it written down like that on another piece of paper I just did not actually solve for it because for some reason my brain was just thinking 1.21/19.3.