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# An 18-karat gold bracelet has a mass of 2.0 ounces. It it is 75% pure gold, what is the total mass in grams of the pure gold

An 18-karat gold bracelet has a mass of 2.0 ounces. It it is 75% pure gold, what is the total mass in grams of the pure gold?

Her teacher gave her the following formulas:
1g = 16 ounces
1 pound= 454 kg

We easily figured out that there are two parts to the formula and used inverse proportionate ratios to calculate this:

?mass of pure gold.

?mass of pure gold=  2.0 X  1 lb.    X  454 kg
______    ________
16 oz.        1 lb.

We got the answer but, it came out to 0.017 g/cm3, but we have no idea where to go next to get the percentages of the gold to 100%.  Could you please give us a few ideas to help us along?  Thank you so much!

Thanks,
Aj
???

### Re: Hi, Aj here...

kyle1990 Mon, 01/26/2009 - 11:56

0.017g/cm^3 is density, not mass. I don't see why her teacher gave her 1lb=454 kg because it is not necessary, at least that's how I see it.
If the bracelet has a mass of 2.0 ounces, then the mass of this in grams is 2 oz / 16 oz/g = .125g. And if 75% of the mass is pure gold...then the total mass of pure gold is
75% X .125g = 0.94g of gold

Show me how you came to the conclusion of 0.017g/cm^3. I'm not sure how you arrived at that

### Re: Hi, Aj here...

saad_ny Mon, 01/26/2009 - 15:09

Hi, teachers...

This is actually my studygroups homework problem (Hudson Valley Comm College)- she spent time trying to figure it out and her teacher gave her some formulas to help her out.  She finally asked her big bro and he couldn't help either, and I have no clue where to start for this!  I've been working on it for over an hour.  Here's the prob:

An 18-karat gold bracelet has a mass of 2.0 ounces. It it is 75% pure gold, how many grams of pure gold are in the bracelet?

Her teacher gave her the following formulas:
1 lb. = 16 ounces
1 kg=2.2051 lb.
1 pound= 454 kg
1 ounce =0.0625 pounds
1 pound = 453.59237 grams

We easily figured out that there are two parts to the formula and used inverse proportionate ratios to calculate this:

?mass of pure gold.

?mass of pure gold=  2.0 oz. X  0.0625 lbs.    X  453.59237 grams
________          __________
1 oz.                    1 lb.

= 0.125 X 453.59237

We got the answer but, it came out to 0.017 g/cm3, but we have no idea where to go next to get the percentages of the gold to 100%.  Could you please give us a few ideas to help us along?  Thank you so much!

Thanks,
Aj

### Re: Hi, Aj here...

kyle1990 Mon, 01/26/2009 - 15:26

It doesn't seem logical to convert the mass of a bracelet into kilograms.