Gold is the basis for the Zakah of cash

About Zakah Nisaab you said a min. 85gms of gold of 595gms of silver, possession for a whole lunar year. When we check the cash value of these two pure metals we found a lot of difference. For example London Bullion market shows 361 USD for one ounce of gold and 5 USD for one ounce of silver. Please guide us how to solve this problem of difference.

Praise be to Allah, the Lord of the Worlds; and may His blessings and peace be upon our Prophet Muhammad and upon all his Family and Companions. The change in the value of gold and silver does not have any affect on the Nisaab of Zakah. The values of these metals have been changing throughout history. Whoever possesses 595 grams or more silver has to pay its Zakah after completing a lunar year. And any person who owns 85 grams or more of gold has to pay Zakah if this meets the conditions. If one possesses cash (bank notes) he has to pay the Zakah of his amount if it reaches the value of 85 grams of gold. The reason for making gold as criterion to pay Zakah is to avoid causing hardship to those who possess money, since common people who are not rich also possess the Nisaab in silver. However, some scholars are of the opinion that the value of silver should be made as criterion to pay the Zakah for the beneficial of needy people. But the preponderant opinion is that gold is the criterion for paying the Zakah of cash. Allah knows best.