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Sat 25 Oct, 2014 03:03 pm
Here is a problem with solution. I don't understand parts of the solution:
In a quantity of metal, the brass is 10 pounds more than 2/3 of the total, the iron 4 1/2 pounds less than 1/6 of the total, and nickel 2 pounds less than 1/7 of the brass. Calculate amount of metal.
Let x = total
2x/3 + 10 = brass
x/6 - 4 1/2 = iron
2x/21 + 10/7 - 2 = nickel *
2x/3 + x/6 + 2x/21 + 10/7 + 3 1/2 = x
4x + x + 4x/7 + 60/7 + 21 = 6x *
4x/7 + 60/7 + 21 = x *
4x + 60 + 21 * 7 = 7x *
60 + 21 * 7 = 3x
20 + 7 * 7 = x
69 = x
* I don't understand what the 2x/21 is.
* I don't understand these steps in solution.
@Randy Dandy,
Quote:... nickel 2 pounds less than 1/7 of the brass.
Brass is 2x/3 + 10, so Nickel is two pounds less than 1/7 of that. 1/7 of the original is 2x/21 + 10/7.
Quote:4x + x + 4x/7 + 60/7 + 21 = 6x *
Not sure where you got this but this is a less than optimum way to do this. You should multiply both sides by 42 to simply, but for some reason you multiply by 6 in this step and 7 later on. All you are doing here is simplifying so you can easily combine terms.
@engineer,
'Brass is 2x/3 + 10, so Nickel is two pounds less than 1/7 of that. 1/7 of the original is 2x/21 + 10/7."
I still don't understand.
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