Answer: 5 
Explanation:
First, write the experimental probability as a fraction in simplest form.
P(glazed donut)
= 
glazed donuts
total
= 
3
2+2+5+3
= 
3
12
= 
1
4
The experimental probability is 
1
4
.
We can predict the outcome of the second set of trials by assuming that the ratio will be the same as in the first set of trials. Write a proportion by setting the two ratios equal to each other, then solve.
1
4
= 
n
20
1
4
(420)
= 
n
20
(420) Multiply both sides by (420)
120
= 4n Simplify
20
= 4n Simplify
5
= n Divide both sides by 4
You would expect 5 out of the next 20 donuts Brenna eats to be glazed donuts.