Percent by mass of platinum in white gold = 100% - 45% = 55%
We let x be the mass of the white which is 45% gold and 55% platinum.
Mass of gold in white gold = m x 0.45
where m is the total mass.
From the given above, we formulate the equation that would allow us to determine the mass of white gold.
154 = x (0.45)
x = 342.22 g
Then, we determine the amount of platinum.
mass of platinum = (342.22 g)(0.55)
mass of platinum = 188.22 grams
Thus, 188.22 grams of platinum is needed.
