Question

Example:
In a school, 12% of the students are first graders. What is the probability that a randomly chosen student will not be a first grader?

Solution:
The students are either first graders or not first graders, so the events are complementary. We know that the two probabilities add to 1, or 100%.

P(event) + P(not event) = 100%
P(1st) + P(not 1st) = 100% • To find the probability of P(red), subtract P(blue) from both sides of the equation.
P(not 1st) = 100% - P(1st) • Subtract P(1st) from each side of the equation.
P(not 1st) = 100% - 12%
P(not 1st) = 88%• Subtract
Plz Explain

Answer 1

Ok so this is an example given to mw by a teacher can you please explain how to do this im confused!

Answer 2

Say you have 100 students that you are working with. Of those 100, 12 are first graders (because 12 is 12% of 100). You want to figure out what the probability is that you will randomly grab one of the students that aren't in 1st grade. Because you don't care what grade they are in as long as they aren't in first grade, the others in the room are all in the same category (the "not event").

You have to take away the number of first graders since you don't want any of those. 100 - 12 = 88 so there are 88 students that aren't in first grade. You have an 88/100 chance that you grab a student not in first grade. 88/100 = 88%.

Let me know whether or not that helped and I can try and break it down for you more if you need.

Answer 3

Ok. so all i do is subtract 12 from 100 and that gives me 88 %

Answer 4

In this case, yes. There are more complex problems where you would have to do more, but because there is only a yes or no, you can do that.

Answer 5

thanks!

Answer 6

no problem