Thread: Simple statistics question

The question goes...

If 85% of people have a bowl of cereal for breakfast, 60% of people have some toas for breakfast, and 50% of people have both cereal and toast for breakfast, what proportion of people have neither cereal nor toast for breakfast?

I know it's simple, but I can't remember how to do it can anyone help?

My preliminary guess (educated, obviously) was 27.5%...

Let C=cereal T=Toast N=No breakfast

P(C) = 0.85 P(T) = 0.60 P(CnT)=0.5

=> P(CuT) = P(C) + P(T) - P(CnT)
= 0.85 + 0.60 - 0.5
=0.95
therefore neither is:

P(N)=1-0.95 = 0.05
P(N)=5%