Q14:
Six cards numbered from 1 to 6 are placed in an empty bowl.First one card is drawn and then put back into the bowl; then a second card is drawn.If the cards are drawn at random and if the sum of the numbers on the cards is 8, what is the probability that one of the two cards drawn is numbered 5 ?
A.
1/6B.
1/5C.
1/3D.
2/5E.
2/3
Q36:
If a and b are positive integers such that a – b and
are both even integers, which of the following must be an odd integer?
a. a/2; b. b/2; c. (a+b)/2; d. (a+2)/2; e. (b+2)/2作者: captain_mas 时间: 2010-12-3 21:05
第一题选D
第二题不全吧？
选D
a-b=even
=> either both are even or both are odd
a/b=even=2x
=> a and b are both even
'a' must have atleast two 2s as factors.
so a/2 is even and a/2+1 is odd作者: abixiaoxinyue 时间: 2010-12-4 06:54
非常感谢！但第一题为什么选D呢？谢谢！
哦第二题是
Q36:
If a and b are positive integers such that a – b and a/b
are both even integers, which of the following must be an odd integer?
a. a/2; b. b/2; c. (a+b)/2; d. (a+2)/2; e. (b+2)/2作者: abixiaoxinyue 时间: 2010-12-4 06:54
