1. ## Need quick confirmation about formula

A chemist is studying the properties of a bronze alloy (mixture) of copper and tin. She begins with 2kg of an alloy that is one-half tin. Keeping the amount of copper constant, she adds small amounts of tin to the alloy. Letting x be the total amount of tin added,
C(x) = Concentration of tin = Total amount of tin/Total amount of alloy

a) Find a formula for C(x)

Is the answer for a); C(x) = x/(2 + x) or is it something different? Please correct me if I am wrong. Thank you.

2. Originally Posted by florx
A chemist is studying the properties of a bronze alloy (mixture) of copper and tin. She begins with 2kg of an alloy that is one-half tin. Keeping the amount of copper constant, she adds small amounts of tin to the alloy. Letting x be the total amount of tin added,
C(x) = Concentration of tin = Total amount of tin/Total amount of alloy

a) Find a formula for C(x)

Is the answer for a); C(x) = x/(2 + x) or is it something different? Please correct me if I am wrong. Thank you.
1+x on the denominator because the alloy already contains 1kg of tin and 1 kg of copper

3. Wait shouldn't it be 2+x in the denominator because they said C(x) = Concentration of tin = Total amount of tin/Total amount of alloy?

4. Originally Posted by florx
Wait shouldn't it be 2+x in the denominator because they said C(x) = Concentration of tin = Total amount of tin/Total amount of alloy?
The 2 kg she begins with includes 1kg tin already So the "total amount of alloy" is only 1kg more than the "total amount of tin". The equation has the domain x >=1.

Actually just reread the question. The question said "let x be the amount of tin added. So formula should actually be (x+1)/(x+2) where x>=0

5. Thank you for your help.