112,783 expanded form

 100,000+ 10,000+ 2,000+ 700+ 80+ 3    

p = 43.75%.

Step-by-step explanation:

Suppose that student 1 arrives before the other.

The probability that student 1 arrives during the first 3/4 hour is 0.75. Then, he will wait 1/4 hour.

The probability that he arrives during the last 1/4 hour is 0.25, and then (on average he will wait) 1/8 hour. So altogether the student 1 will wait

(0.75)*(1/4) + (0.25)(1/8) = 0.21875.

Then, the probability that student 2 arrives while the student 1 is waiting is 0.21875.

In the same way, if student 2 arrives before student 1.

The probability is

p = (0.21875) + (0.21875) = 0.4375

⇒ p = 43.75%.