a rational number can be written in form form a/b where a and b are integers and b≠0
remember that a rational number times an irrational number=irrational
irrational numbers can't be in a/b form
so
A. pi doesn't work, that's irrational
B. this works, we can say 2.22=222/100, when multplied by 0.5, we get 111/100 which is still rational
C. nope
D. we can write this as 2000/999 so it is rational, when multiplied by 0.5, we get 1000/999 which is still rational
answers are B and D
