power prep question

[jing]

hi

somebody help to solve this

Two different integers are to be selected from a set of 10 different integers in which half of the integers are even and half are odd. how many of the 45 possible selection consists of one even and one odd integer.

choices are
a) 5
b) 10
c) 20
d) 23
e) 25

correct answer is e

[spiderman]

you have 5 even and 5 odd numbers.

no. of ways of selecting one even = 5C1 = 5
no. of ways of selecting one odd = 5C1 = 5
hence no. of ways of selcting one even and one odd = 5*5 = 25.

[jing]

thanks spiderman