Using the digits 1, 2, 3 and 5, how many 4 digit numbers can be formed if
a) The first digit must be 1 and repetition of the digits is allowed?
b) The first digit must be 1 and repetition of the digits is not allowed?
My thinking:
a) chose 1 then 2,3,5 can have 3^3 ways to form numbers. The answer is 27
b) chose 1 then 2,3,5 can have 3! ways to form numbers without repeating numbers. The answer is 6.
Am I right?
a) The first digit must be 1 and repetition of the digits is allowed?
b) The first digit must be 1 and repetition of the digits is not allowed?
My thinking:
a) chose 1 then 2,3,5 can have 3^3 ways to form numbers. The answer is 27
b) chose 1 then 2,3,5 can have 3! ways to form numbers without repeating numbers. The answer is 6.
Am I right?