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30% of all students are in a play at school. All students except for 140 are in the play. How many students are in the school?

I need to write the equation and solve it for this problem


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Ellen S. | Math and Writing GeekMath and Writing Geek
4.8 4.8 (79 lesson ratings) (79)
The key to this one is figuring out what percent of the students are NOT in the play.  If 30% of the students are in the play, that means that 70% are not, right?  And we know that 140 students are not in the play.  So 140 people is 70% of the total students, which is what we want to find out.
For a problem like this, I always set it up as a proportion.  Remember that 100% is the whole thing.
140/70 = x/100    (partial number/partial percent = whole number/whole percent)
2 = x/100
x = 200
So there are 200 students in the school.