In a committee, 50 people speak French, 20 speak Spanish and 10 speak both Spanish and French. The number of persons speaking at least one of these two languages is
60
Let S,F represents the set of people speaking spanish and french languages respectively.
Here n(S)= 20, n(F)=50, n(S∩ F) = 10
Now using,
n(S∪F) = n(S)+n(F)−n(S∩F)
⇒n(S∪F) = 20 + 50 -10 = 60