Santa estimates that 10% of the children in the world have been good this year but do not celebrate Christmas, and that 50% of the children who celebrate Christmas have been good this year. If 40% of the children in the world have been good, what percentage of children in the world are not good and do not celebrate Christmas?

a. 20 %

b. 30 %

c. 40 %

d. 60 %

e. 70 %

Answer: B

Source: Manhattan GMAT