Serial numbers for an item produced in a factory are to be made using two letters followed by four digits (0 to 9). If the letters are to be taken from twenty six letters of English alphabet without repetition and the digits are also not repeated in a serial number, how many serial numbers are possible?

Explanation

In first position from left we have 6 alphabet choices, so in the second position, we will have 5 choices because no repetition is allowed.

On the first position from left for digits or third position from the left of serial number we will have 10 choices,

and for next position, we will have 9 choices, the number of choices will decrease by one as we keep on going right side.
Because on serial numbers we can write zero on the left most position of numbers.

The number of ways in which we can form four digit with two alphabets serial numbers with the help of given data is
`6 xx 5 xx 10 xx 9 xx 8 xx 7 = 151200.`