Copy of Number Properties DS – 11 to 20

If x and y are positive integers such that the product of x and y is prime, what is the units’ digit of 7^x + 9^y?
(1) 24 < y < 32
(2) x = 1

if xy=-6 what is xy(x+y)
1.x-y = 5
2.xy² = 18

Can the positive integer “p” be expressed as the product of two integers, each of which is greater than 1?
(1) 31<p<37
(2) p is odd

Is A + B + C even?
(1) A – C – B is even
(2) (A – C)/B is odd

If i and j are integers, is i + j an even integer?
(1) i < 10
(2) i = j

x, y, and z are consecutive integers, and x < y < z. What is the average of x, y, and z?
(1) x = 11
(2) The average of y and z is 12.5

A school administrator will assign each student in a group of n students to one of m classrooms. If 3 < m < 13 < n, is it possible to assign each of the n students to one of the m classrooms so that each classroom has the same number of students assigned to it?

(1) It is possible to assign each of 3n students to one of m classrooms so that each classroom has the same number of students assigned to it.
(2) It is possible to assign each of 13n students to one of m classrooms so that each classroom has the same number of students assigned to it

If x and y are positive integers such that x = 8y + 12, what is the greatest common divisor of x and y?
(1) x = 12u, where u is an integer.
(2) y = 12z, where z is an integer.

What is the value of n?
(a) n is between 0 and 1.
(b) 7/16 is 3/8 more than n

If d is a positive integer is √d an integer?
(1) d is the square of an integer
(2) √d is the square of an integer