B3 An ounce of gold (31 g) was worth on average 1200 USD in 2010.

A How many euros did an ounce of gold cost in 2010 if 1 EUR was worth 1.3 USD?

B How many USD would a cube of gold with an edge of $2 \mathrm{dm}$ cost if the density of gold is $19.32 \frac{\mathrm{g}}{\mathrm{cm}}$ ?

C By what \% did the price of gold on the world market increase from 2007 to 2010 if the price of gold in 2007 was on average 660 USD per ounce?
In 2010, an ounce of gold (31 g) cost $1200: 1.3 = 923$ EUR. The volume of a cube with a side of 2 dm is 8 $dm^{3}$. Since the density of gold is $19.32 \frac{g}{cm^{3}} = 19.32 \frac{kg}{dm^{3}}$, the mass of such a cube is $m = \rho \cdot V = 19.32 \frac{kg}{dm^{3}} \cdot 8 dm^{3} = 154.56 kg$. The cost of such an amount of gold is $\frac{154.56 kg \cdot 1200 \$}{0.031 kg} = 5982967.74 \$ \approx 5982968 \$$$. The ratio of the price of gold in 2010 to the price of gold in 2007 is $\frac{1200 \$}{660 \$} = 1.82$, which means the price of gold increased by $82 \%$.

A Answer, e.g.: In 2010, an ounce of gold cost 923 EUR. .................................. 1 t

![](https://cdn.mathpix.com/cropped/2024_06_07_8c4ca9fb11cdb9201aa3g-7.jpg?height=57&width=1639&top_left_y=731&top_left_x=268)
Answer, e.g.: The cube would cost 5982968 \$. ..................................................... 2 t

C Answer, e.g.: The price of gold increased by $82 \%$. .......................................... 1 t