Since 1 US Dollar is equal to 319.643234 Sri Lankan Rupees, we could say that n United States Dollars are equal to 319.643234 times n Sri Lankan Rupees. In other words, we could use the following formula:
Sri Lankan Rupees = United States Dollars x 319.643234
For example, let's say that we want to convert 2.0 United States Dollars to Sri Lankan Rupees. Then, we just replace United States Dollars in the abovementioned formula with 2.0:
Sri Lankan Rupees = 2.0 x 319.643234
That is, 2.0 United States Dollars are equal to 639.286468 Sri Lankan Rupees.