Let the total number of students in the class be x. Common Students = 40
72x
100
−40+40+
44x
100
=x ⇒
72x
100
x+
44x
100
x=40 ⇒
16x
100
=40⇒x=
40×100
16
⇒x=250 Alternate Method: Number persons in both = number of persons in 1st + no. of persons in 2nd – Total no. of persons in any one % of persons in both =72+44–100=16% Total no. of persons ×