Question

some debit and credit card companies require their customers to choose personal identification numbers (pins). customers choose 4 digits from 10 possible digits and does not repeat digits. how many different possible pins are there?

Answer 1

for the first digit, we have 10 choices from o to 9. to repeated, we have 10-1= 9 choices Since digits are not for second digit. Similarly, we have 8-1= I choices for third digit and 9-1 = 8 choices for the digit lo ways aways sways I ways So, No. of different possible pins a 10x9x8x7 = 5040