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
People speaking atleast one language are the ones who speak French or Spanish, or both French and Spanish.
From the Venn-diagram, we observe that the number of people speaking atleast one language is n(F∪S).
But, n(F∪S)=n(F)+n(S)−n(F∩S).
=50+20−10
=60