Question

Which expression can be used to decide if x is not between 10 and 20?

a. not (x< 10 or x<20)
b.not (x < 10 and x<20)
c. not (x > 10 or x < 20)
d. not (x > 10 and x < 20)

Answer 1

The correct expression to decide if x is not between 10 and 20 is d. not (x > 10 and x < 20), as it declares x to be outside the range of 10 to 20, including numbers less than or equal to 10 and greater than or equal to 20.

Step-by-step explanation:

To determine which expression can be used to decide if x is not between 10 and 20, we need an expression that is true when x is less than or equal to 10 or greater than or equal to 20. The correct expression to convey 'x is not between 10 and 20' is:

d. not (x > 10 and x < 20)

To explain:

• The expression x > 10 and x < 20 means 'x is greater than 10 and less than 20', which defines x being between 10 and 20.
• By applying the not operator, we are looking for the opposite scenario - where x is not in that range.
• Therefore, not (x > 10 and x < 20) is true whenever x is either less than or equal to 10 or greater than or equal to 20.