Combinatorics 35

How many different positive two-digit integers are there such that the sum of the digits is-prime-11

At a certain college last year, a total of 260 students took College Algebra the fall semester...

Ed's own pump, operating alone at its constant rate, can empty his swimming pool in 15 hours. The...

In a class of 100 students, more students were born in October than in any other month. What is..

A group of 10 people consists of 2 married couples and 6 bachelors. A committee of 4 is to be...

­If 5 integers are to be selected at random and without replacement from the list consisting of...

k is a positive integer. When k^4 is divided by 32, the remainder is 0. Which of the following...

A merchant bought a coat at a wholesale price of $120 and then sold it at a 20 percent discount...

A computer is programmed to play the game of 24 by independently replacing the symbols ▲ and @ in...

For positive integers M and N, if 24 is a divisor of M and 36 is a divisor of N, what is the...

In certain year in Country C, x sets of twins and y sets of triplets were born. If there were z...

How many positive integers less than 500 can be formed using the digits 1, 2, 3, 4, 5, assuming...