[讨论]钱永强数学两道

luodanxuan

 

真是麻烦各位NN们了，终于做到最后一套了，有两个问题还是要请教大家

1. Each of the integers from 0 to 9, inclusive, is written on a separate slip of bank paper and the ten slips are dropped into a hat. If the slips are then drawn one at a time without replacement, how many must be drawn to ensure that the numbers on two of the slips drawn will have a sum of 10?

A) 3   B)4   C)5   D)6   E)7

 

2.There were 36,000 hardback copies of a certain novel sold before the paperback version was issued. From the time the first paperback copy was sold until the last copy of the novel was sold, 9 times as many paperback copies as hardback copies were sold. If a total of 441,000 copies of the novel were sold in all, how many paperback copies were sold?

A) 45,000   B)360,000   C)364,500   D) 392,000   E) 396,000