Question

Thirty percent of all the students in a school are in a Play. All except for 140 students are in the play. How many students are in the school?

Answer 1

Well, if 30% of students are in the play then 100%-30% = 70% of students are not in the play, which is also 140.

So we know:

70%*x=140

70% is also 7/70:

$\frac{7}{10} x=140$

divide both sides by 7 and multiply by 10:

x=20*10

x=200

there are 200 students in the school