Number TheoryMediumHard Number Theory ShareHard Number Theory · Medium problemFor which sum does the formula (p−1)(q−1)2\dfrac{(p - 1)(q - 1)}{2}2(p−1)(q−1) give the wrong value of ∑k=18⌊ak9⌋\displaystyle\sum_{k=1}^{8}\left\lfloor \frac{ak}{9} \right\rfloork=1∑8⌊9ak⌋?Aa=5a = 5a=5Ba=7a = 7a=7Ca=6a = 6a=6Da=2a = 2a=2Check Show answer Walk through it step by step Practice more like this Review this concept