Of the 50 students in a school, 30 have brown hair, 21 have blue eyes, and 9 have both brown hair and blue eyes.

How many students have neither brown hair nor blue eyes?

Not my homework but was on freerice.com and this question popped up..

Answer said 8. Any idea how they got it? It might be cause i'm trying to figure this out at 4am in the morning but I don't get how they're getting 8.

halp , help , welp

#watdafuck

30 have brown hair, among them 9 have brown hair and blue eyes.
30 - 9 = 21 have brown hair but don't have blue eyes.

21 have blue eyes, among them 9 have brown hair and blue eyes.
21 - 9 = 12 have blue eyes but don't have brown hair.

Finally :

9 : brown hair AND blue eyes
12 : blue eyes AND NOT brown hair
21 : brown hair AND NOT blue eyes

50 - (9+12+21) = 50 - 42 = 8 have NEITHER brown hair, NOR blue eyes.

This post was edited by feanur on May 29 2013 09:12am

same result with a slightly different approach

30 + 21 = 51 characteristics, subtracting 9 which have double characteristic gives 51 - 9 = 42 which have either one or both characteristics

which lives 50 - 42 = 8 having neither characteristic