Question

if a two digit number is repeated how many digits can be formed?​

Answer 1

Answer:

Because it's without repetition, so the number that have been filled the first digit cannot be the second digit. Thus, the numbers that is possible to occupy second are 5 digits. Thus, there are 6 x 5 = 30 numbers that can we form from those 6 numbers: 1,2,5,7,8 and 9 without repetition.