How many 4-digit Q numbers (ABCD) can be formed such that |A – D| = 2?
Choose the correct choice from the following answers
A) 2,000	B) 1,900	C) 1,800	D) 1,600	E) 1,500
1) A=0 and D-8   2) A and D as 1 and 9..so 3*100= 
<gadget id="calculator">3*100</gadget>
<output>300</output>
300 extra ways ans  1800-300= 
<gadget id="calculator"> 1800-300</gadget>
<output>1_500</output>
1500.   we are looking for |A-D|=2 so any of the two can be bigger..   these two can have values (1,3) ; (2,4) so on till (7,9) so total 7*2 = 14..   another arrangement could be A as 2 and D as 0... D as 2 and A as 0 is not possible as number will become 3 digits..   so the ways A and D can be placed = 14+1= 
<gadget id="calculator">14+1</gadget>
<output>15</output>
15 ways..   B and C can be placed in 10*10 ways..   Total Q= 15*10*10=1500.1,500
<result>E</result>
How many 4-digit Q numbers (ABCD) can be formed such that |A – D| = 2?