ACT Quiz 17 - LL - Number Concepts and Properties

How many prime numbers are there between 20 and 40?

• 4

• 5

• 6

• 7

• 8

• 98

• 49

• 14

• 7

• 2

If the product of two numbers is equal to 1, the numbers are reciprocals. If a and b are reciprocals and a > 1, then b must be:

• greater than 1

• between 0 and 1

• equal to 0

• between 0 and -1

• less than -1

Which of the following is true for all consecutive integers a and b such that a < b?

• a < 0

• b > 0

• a + b is even

• a² - b² is odd

• a² + b² is even

If the product of 7 integers is positive, at least how many of these 7 integers must be positive?

• 1

• 2

• 3

• 4

• 5

What is the least common multiple of 4, 2x, 8y, and 5xy?

• 8xy

• 16xy

• 32xy

• 40xy

• 320x²y²

• 25

• 23

• 20

• 18

• 15

When x, y, and z are real numbers and x²y⁶z > 0, which of the following must be greater than 0?

• xy

• xz

• zy

• xyz

• x²z

• -621

• -63

• -62

• -7

• -6