If two 2-digit positive integers have their respective tens digits exchanged, the difference between the pair of integers changes by 4. What is the greatest possible difference between the original pair of integers?  Choose the correct choice:
A) 76	B) 80	C) 82	D) 90	E) 94
For maximizing most of 2 digit integer questions, you will have numbers closes to 90s and 10s.   Start with 10 and 99 you see that the differences are 89 (=99-10) and 71 (=90-19) giving you a change of 89-71= 
<gadget id="calculator">89-71</gadget>
<output>18</output>
18, a lot more than 4.   Next check with 15 and 99, you get 84 (=99-15) and 76 (=95-19), you get 84-76= 
<gadget id="calculator">84-76</gadget>
<output>8</output>
8. Thus the difference has been decreasing.   Finally check with 99 and 17, you get 82 (=99-17) and 78 (=97-19), giving you 82-78= 
<gadget id="calculator">82-78</gadget>
<output>4</output>
4 . This is the answer.   Thus, the maximum difference is 99-17= 
<gadget id="calculator">99-17</gadget>
<output>82</output>
82. 82 is the correct answer.
<result>C</result>
If two 2-digit positive integers have their respective tens digits exchanged, the difference between the pair of integers changes by 4. What is the greatest possible difference between the original pair of integers?