a manufacturers serial number consists of 2 letters of the alphabet and 3 numbers. How many serial numbers are possible?
+33653 If both letters are different and all the numbers are different then there are 5! = 120 different possibilities.
If both letters can be the same,then there are 5!/2! ways.
If both letters can be the same and the three numbers can be the same then there are 5!/(2!*3!) ways.
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