1:In the equation above, k,r,s,t, and v represent positive numbers. Multiplying which one of these numbers by 2 will reduce the value of n to1/2 of its present value?
后半句啥意思?翻译一下
选项分别是k,r,s,t,v
2: A certain money market account that had a balance of $48,000 during all of last month earned $360 in interest for the month. At what simple annual interest rate did the account earn interest last month?