Prep-1-ps36

36.    4841-!-item-!-187;#058&004235

In a certain deck of cards, each card has a positive integer written on it.  In a multiplication game, a child draws a card and multiplies the integer on the card by the next larger integer.  If each possible product is between 15 and 200, then the least and greatest integers on the cards could be

(A) 3 and 15

(B) 3 and 20

(C) 4 and 13

(D) 4 and 14

(E) 5 and 14

Ans:C

有沒有人知該如何解?

假设最小数为A，那么A是满足A×(A+1)>15的最小正整数，A＝4

假设最大数为B，那么B是满足B×(B+1)< 200 的最大正整数，B＝13