Is it permissible to exchange 9 metal riyals for 10 paper riyals, and is this considered usury (riba)?

Some scholars permit exchanging paper currencies for metal currencies with a premium, considering each type a different genus. Therefore, there is no usury in this exchange if it is done hand-to-hand, as ruled by the Permanent Committee for Issuing Fatwas and Sheikh Ibn 'Uthaymeen. Others hold that equality between them is obligatory as a precautionary measure and to avoid dispute. There is no blame upon an ordinary person for acting upon the opinion of some scholars in matters of differing opinions.