Phone numbers are 10 digits long. How many possible phone numbers are there if the 1^st and 4^th numbers can't be 0?

A student formed a club at their school. They have 13 members, and need to elect a president, vice president, and treasurer. How many ways are there to fill these officer positions?

Emily is organizing her closet. She has 15 shirts left to hang but has space in one section for 6 shirts. How many ways could she hang shirts in that section?

Evaluate the given expression. ${}_9{P}_4$

How many ways are there to arrange the letters in the word CALCULUS?

From a class of 28 students, in how many ways could a teacher select 4 students to lead the class discussion?

Evaluate the given expression. ${}_{11}{C}_7$

Find the term indicated in each expansion. (x − 1/2)⁹; fourth term