How many 3 digit integers can be chosen such that none of the digits appear more than twice and none of the digits equal zero ?	Pick one:
A) 729	B) 720	C) 648	D) 640	E) 57
number of ways without restriction = 9*9*9= 
<gadget id="calculator">9*9*9</gadget>
<output>729</output>
729   number of ways that break restriction= 9*1*9 = 9   so the answer is   729-9= 
<gadget id="calculator">  729-9</gadget>
<output>720</output>
720   ANS:720
<result>B</result>
How many 3 digit integers can be chosen such that none of the digits appear more than twice and none of the digits equal zero ?