1) Pure gold is not a hard metal. To make it harder , some other metals are added to make an alloy. The purity of gold is represented by "K". For example, 24K is pure gold, and 18K means the alloy contains gold and other metals in the ratio 18:6.
Which of the following contains more gold : a 18K golden necklace of 24g, or a 14K golden necklace of 30.6 g ?
列式PLZ*
Maths(ratio,,20 fun)
2007-11-03 4:46 am
回答 (3)
2007-11-03 4:55 am
✔ 最佳答案
首先你要知18k金的黃金成份係佔成條頸鍊的18/(18+6)=3/4而 14K 金的黃金成份係佔成條頸鍊的14/(18+6)=7/12
咁就計佢地黃金的重量:
a 18K golden necklace of 24g有黃金:
24x3/4=18g
而a 14K golden necklace of 30.6 g有黃金:
30.6x7/12=17.85g
so a 18K golden necklace of 24g的黃金成份比a 14K golden necklace of 30.6 g多0.15g黃金
2007-11-03 4:57 am
Let the gold in the 18K necklace be x g
and the gold in the 14K necklace be y g.
For the 18K necklace, the ratio of gold and other metals is
18:6 = x:(24-x)
=> 6 * x = (24-x) * 18
=> 6x = 432 - 18x
=> 24x = 432
=> x = 18
In the 18K necklace, there is 18g gold.
For the 14K necklace, the ratio of gold and other metals is
14:6 = y:(30.6-y)
=> 6 * y = (30.6-y) * 14
=> 6y = 428.4 - 14y
=> 20y = 428.4
=> y = 21.42
In the 14K necklace, there is 21.42g gold.
21.42 > 18
=> The 14K necklace contains more gold.
and the gold in the 14K necklace be y g.
For the 18K necklace, the ratio of gold and other metals is
18:6 = x:(24-x)
=> 6 * x = (24-x) * 18
=> 6x = 432 - 18x
=> 24x = 432
=> x = 18
In the 18K necklace, there is 18g gold.
For the 14K necklace, the ratio of gold and other metals is
14:6 = y:(30.6-y)
=> 6 * y = (30.6-y) * 14
=> 6y = 428.4 - 14y
=> 20y = 428.4
=> y = 21.42
In the 14K necklace, there is 21.42g gold.
21.42 > 18
=> The 14K necklace contains more gold.
2007-11-03 4:55 am
(18 divide by 24):(14 divide by 30.6)
0.75:38.8
So 14K golden necklace of 30.6 g contains more gold
0.75:38.8
So 14K golden necklace of 30.6 g contains more gold
收錄日期: 2021-04-13 14:19:55
原文連結 [永久失效]:
https://hk.answers.yahoo.com/question/index?qid=20071102000051KK03122