The formula to calculate the value of gold is:
\[ \text{Total Pure Gold} = \text{Weight of 18-karat gold} \times \frac{18}{24} + \text{Weight of 9-karat gold} \times \frac{9}{24} \]
\[ \text{Total Value} = \text{Total Pure Gold} \times \text{Current Gold Price per Gram} \]
Assuming you have found a box of old gold jewelry divided into two batches: 18-karat gold weighing 120 g and 9-karat gold weighing 350 g. The current gold price is $39 per gram.
Calculate the pure gold content:
\[ \text{Pure Gold in 18-karat batch} = 120 \, \text{g} \times \frac{18}{24} = 90 \, \text{g} \]
\[ \text{Pure Gold in 9-karat batch} = 350 \, \text{g} \times \frac{9}{24} = 131.25 \, \text{g} \]
Total pure gold:
\[ 90 \, \text{g} + 131.25 \, \text{g} = 221.25 \, \text{g} \]
Total value:
\[ 221.25 \, \text{g} \times \$39/\text{g} = \$8,628.75 \]
Your box of gold jewelry is worth $8,628.75!