Question

In a survey of some students, it was found that $60\%$ of the students were studying commerce and $40\%$ were studying science. If 40 students were studying both the subjects and $10\%$ did not study any of two subjects, by drawing a Venn diagram, find :
i) the total number of students
ii) the number of students who were studying science only

Answer 1

Let total number of students be x
i) $0.6x+0.4x-40+0.1x=x$
$\Rightarrow x=400$
ii) Students studying science only $=0.4x-40$
$=0.4\times 400-40$
$=160-40$
$=120$