#1**+2 **

87.

Since there are three digits and each digit has 10 options,

there are a total of:

10^3 ways of identifying students.

The first number can be a 0, since it is not supposed to be a number, just an identification.

10^3 = 1000

That is you final answer.

GYanggg
Apr 25, 2018

#2**+2 **

88.

There are a total of:

\(\binom{15}{4}\)

ways to choose the debaters.

This is equal to 1365.

Since we need those four people, with only one way to choose them.

The chance this will happen is 1/1365.

GYanggg
Apr 25, 2018