Here, n(total) = 400
n(chess ) = 18, n(TT) = 20, n (carom) = 27.
n(chess & TT)=7, n(TT & carom)= 12 and n(Chess & Carom)=?
n(chess & TT & carom)=4
We have,
n(total) = n(chess) + n(TT) + n (carom)-n(chess & TT) - n(TT & carom)- n(chess & carom) +
n(chess & TT & carom)
40=18+20+27-7-12-n(chess & carom) + 4
n(chess & carom) = 50 - 40 = 10
So, total number of students who play both chess & carom is = 10.
But there are 4 students who play all the three games. So, the number of students who play chess and carom but not table tennis = 10-4=6. ans.