How many numbers with 4 different digits can be formed using only the odd digits?  Answers:
A) 10
B) 20
C) 40
D) 60
E) 120
Odd digits are 1, 3, 5, 7, 9.   We want 3 different digits.   First digit can be chosen in 5 ways.   Second digit can be chosen in 4 ways.   Third digit can be chosen in 3 ways.   Fourth digit can be chosen in 2 ways.   Total ways = 5*4*3*2= 
<gadget id="calculator">5*4*3*2</gadget>
<output>120</output>
120   Hence option (120).
<result>E</result>
How many numbers with 4 different digits can be formed using only the odd digits?