Problems(2)
For how many positive integers n does 1 \plus{} 2 \plus{} \cdots \plus{} n evenly divide from 6n?
<spanclass=′latex−bold′>(A)</span> 3<spanclass=′latex−bold′>(B)</span> 5<spanclass=′latex−bold′>(C)</span> 7<spanclass=′latex−bold′>(D)</span> 9<spanclass=′latex−bold′>(E)</span> 11 Forty slips are placed into a hat, each bearing a number 1, 2, 3, 4, 5, 6, 7, 8, 9, or 10, with each number entered on four slips. Four slips are drawn from the hat at random and without replacement. Let p be the probability that all four slips bear the same number. Let q be the probability that two of the slips bear a number a and the other two bear a number b\not\equal{} a. What is the value of q/p?
<spanclass=′latex−bold′>(A)</span> 162<spanclass=′latex−bold′>(B)</span> 180<spanclass=′latex−bold′>(C)</span> 324<spanclass=′latex−bold′>(D)</span> 360<spanclass=′latex−bold′>(E)</span> 720 ratioprobability