Saturday, August 24, 2002

By: Laura Luckasavitch

Subject: Math - fractions, percent, simple algebra, cross multiplying, problem solving

Grades - Ontario Curriculum:

Grade 8 - Number Sense and Numeration

Grade 9 - Number Sense and Algebra

For the Olympics, gold medals are awarded to the first place, silver to the second, and bronze to the third. But are these medals actually made out of the mineral that they are named after? The gold and silver medals are both made of silver. The gold medals are then coated with gold. Each Olympic gold medal is made up of 210g of silver and is coated with 6g of 24 carat gold. The bronze medals are made of copper, zinc, tin, and a very small amount of silver. In the Sydney 2000 Olympics and the Paraolympic Games, each bronze medal contained 1% silver and the remaining 99% was made from coinage bronze. Bronze coinage is made up of 97% copper, 2.5% zinc, and 0.5% tin. This bronze came from Australian currency, which is no longer in circulation.

Information here was originally taken from the Minerals Council of Australia website.

Student Questions and Answers

1. What % of the gold medals are actually gold? Silver?

Gold: 6 / 216 = 2.8%

Silver: 210 / 216 = 97.2%

2.How much gold is actually needed to make 50 gold medals? How much silver is needed?

Gold: 6g x 50 = 300g

Silver: 210g x 50 = 10500g or 10.5kg

3.How much gold is actually needed to make 90 gold medals? How much silver is needed?

Gold: 6g x 90 = 540g

Silver: 210g x 90 = 18900g or 18.9kg

4. Pure gold is 24 carats (k). 10k gold means that the gold is 10 / 24 parts pure and that 14 parts are other metals, usually composed of copper and zinc. These metals give the gold object it’s hardness. What percent of 10k gold is pure gold? 14k? 18k? 24k?

10k: 10k / 24k x 100% =

41.7% pure gold

14k: 14k / 24k x 100% =

58.3 % pure gold

18k: 18k / 24k x 100% =

75% pure gold

24k: 24k / 24k x 100% =

100% pure gold

5. If 10k gold was used instead of the 24k gold, how much real gold would be in 1 gold medal? Give your answer in percentage and grams.

10k / 24k = 41.7 % real gold

0.417 x 6g = 2.5g real gold per medal

2.5g / 216g = 1.2% real gold per medal

6. If 18k gold was used instead of the 24k gold, how much real gold would be in 1 gold medal? Give your answer in percentage and grams.

18k /24k = 75% real gold

0.75 x 6g = 4.5g real gold per medal

4.5g / 216g = 2.1% real gold per medal

More Challenging Questions

7. If the bronze medal has the same mass as the gold medal, how much silver, copper, zinc, and tin will be needed for 1 bronze medal?

Silver: 1% / 100% = xg / 216g

x = 2.2g

Copper + Zinc + Tin = 216g - 2.2g = 213.8g

Copper: 97% / 100% = xg / 213.8g

x = 207.4g

Zinc: 2.5% / 100% = xg / 213.8g

x = 5.3g

Tin: 0.5% / 100% = xg / 213.8

x = 1.1g

8. How much silver, copper, zinc, and tin would be needed for 50 bronze medals?

Silver: 2.2g x 50 = 110g

Copper: 207.4g x 50 = 10370g or 10.37kg

Zinc: 5.3g x 50 = 265g

Tin: 1.1g x 50 = 55g

9. If no silver was used in the bronze medals and only the coinage bronze was used, how much copper, zinc, and tin would be needed for 1 bronze medal?

Copper: 97% / 100% = xg / 216g

x = 209.5g

Zinc: 2.55 / 100% = xg / 216g

x = 5.4g

Tin: 0.5% / 100% = xg / 216g

x = 1.1g