How many integerskgreater than 100 and less than 1100 are there such that if the hundreds and the units digits ofkare reversed, the resulting integer is k+99?  Choose the correct choice from the following answers.
A) 50  B) 60  C) 70  D) 80  E) 90

Rationale: numbers will be like 102 = > 201 = 102 + 99 203 = > 302 = 103 + 99 so the hundereth digit and units digit are consecutive where unit digit is bigger than hundred digit . there will be ninet pairs of such numbers for every pair there will 10 numbers like for 12 = > 102 , 112,132 , 142,152 , 162,172 , 182,192 . total = 9 * 10 = 90 hence e .
Answer: E