SOLUTION: In 60 ounces of alloy for watch cases there are 20 ounces of gold >how much copper must be added to the allow so that a watch case weighing 4 ounces , made from the new allo, will

Algebra ->  Coordinate-system -> SOLUTION: In 60 ounces of alloy for watch cases there are 20 ounces of gold >how much copper must be added to the allow so that a watch case weighing 4 ounces , made from the new allo, will       Log On


   

Question 1062376: In 60 ounces of alloy for watch cases there are 20 ounces of gold >how much copper must be added to the allow so that a watch case weighing 4 ounces , made from the new allo, will contain exactl 1 ounce of gold
Answer by josmiceli(19441) About Me  (Show Source):
You can put this solution on YOUR website!
Originally, gold/aloy = 20/60 = +1%2F3+
4 ounces of the alloy has
+4%2A%281%2F3%29+=+4%2F3+ ounce of gold
+4%2A%282%2F3%29+=+8%2F3+ ounces of alloy
---------------------------
+%28+4%2F3+%29+%2F+%28%28+8%2F3+%2B+x+%29%29+=+1%2F4+
+4%2F3+=+%281%2F4%29%2A%28+8%2F3+%2B+x+%29+
+4%2F3+=+8%2F12+%2B+%281%2F4%29%2Ax+
multiply both sides by +12+
+16+=+8+%2B+3x+
+3x+=+8+
+x+=+8%2F3+
2.667 ounces of copper must be added
to the 4 ounces of alloy
---------------------------
check:
+%28+4%2F3+%29+%2F+%28%28+8%2F3+%2B+x+%29%29+=+1%2F4+
+%28+4%2F3+%29+%2F+%28%28+8%2F3+%2B+8%2F3+%29%29+=+1%2F4+
+4%2F16+=+1%2F4+
+1%2F4+=+1%2F4+
OK
Check the math & get another opinion, too