Question

How many two-digit positive integers can be formed from the digits 1, 5, 6, and 8 if no digit is repeated?

Answer 1

Write out all of the 2-digit positive integers formable from 1, 5, 6 and 8, without repetition of digits (e. g., no '22'):

15, 16, 18

Now write out the 2-digit pos. int. that begin with 5:  51, 56, 58.

And so on.

Remember that you can also form 2-dig. pos. int. beginning with 6 and beginning with 8.

Count how many 2-dig. pos. int. you have created.  That's your answer.

Answer 2

Answer:

The total number of ways to form a two number without repetition is 12.

Step-by-step explanation:

The given digits are 1, 5, 6 are 8. Total number of digits is 4.

We have to form a two digit number without repeating a digit. So, the total ways to choose a number for first place is 4.

Since repetition is not allowed, therefore the total ways to choose a number for second place is 3.

Total number of ways to form a two number without repetition is

$4\times 3=12$

Therefore the total number of ways to form a two number without repetition is 12.