1、If x and y are integers and xy0, what is the remainder when x is divided by y?
when x is divided by 2y, the remainder is 4;
when x+y is divided by y, the remainder is 4;
【答案】B
【思路】X=2YK+4 舉反例：當Y=4，X=4時，X/Y的餘數爲0。當Y=3，X=10時,X/Y的餘數爲1. X+Y=YK+4 則X=Y+4, 所以X/Y的餘數爲4
2、One set of numbers consists of consecutive integers and the least number is 3. How many numbers are there in the set?
The average of all the numbers in the set is 6;
The number of integers is one more than the range of the set.
【答案】A
【思路】設最大的數爲X, 則共有個數字, 利用求和公式, /=6, 則X=9, 所以這個集合共有7個數字. The number of integers爲, one more than the range of the set爲, 兩邊一樣的，無法求出X.
3、1010的table裏每個格里只能放-100， 0， 100這3個數中的'一個，問sum of the table entries0?
每一行只有一個是正數;
每一列只有一個是正數;
【答案】E
【思路】無論是或, 還是+,都無法確定整個表格的和,因爲在每個格中都放0,或100或-100或每一行只有一個是正數100,其他還是可以隨便放,可都放0或-100,結果就不同,前者和大於0,後者和小於0.同樣地條件一和二都無法確定和的正負情況.
