A Swedish watch company is assigning ID cards for its employees. The ID is made of 7 digits. How many ID numbers can exist such that at least one of the digits repeat?
Options:
A .  9456745
B .  7898760
C .  8455680
D .  None of these
E .  none of these
Answer: Option C : C Total number of combinations = No repeats + 1 number repeat + 2 number repeat +.....7 number repeat Total number of combinations - No repeats = 1 number repeat + 2 number repeat +...... 7 number repeat Total number of combinations - No repeats = Atleast one number repeat 106×9−(9.9.8.7.6.5.4)=9000000−544320=8455680
Submit Comment/FeedBack