Alloy weighing 270g with 5% gold content was melted into an alloy with 10% gold content.

Alloy weighing 270g with 5% gold content was melted into an alloy with 10% gold content. Determine and write down in response the number of grams of gold that you need to add.

First, we find the mass of the alloy, excluding gold.

270 * 0.05 = 13.5 (grams) – the mass of gold in the alloy.

270 – 13.5 = 256.5 (grams) – the mass of the alloy without gold.

Since in the new alloy the percentage of gold will be 10%, we can find the percentage of the alloy without it.

100 – 10 = 90%

Hence we have: 256.5 = 90%; x (mass of new alloy) = 100%

x = 256.5 * 100: 90 = 25650: 90 = 285 (grams) – a new alloy.

Now let’s calculate how much the mass has changed after remelting.

285 – 270 = 15 (grams)

Answer: 15 grams.