# Truth Tables and De Morgan's Rules

## 15. Oil Change

Answer:Using the De Morgan Rule

`!(A && B)`

is equivalent to`!A && !B`

the original expression

while ( !(input.equals( "quit" ) || (count > limit)) ) { . . . }is equivalent to

while ( !input.equals( "quit" ) && !(count > limit)) ) { . . . }which is equivalent to

boolean reject = (speed <= 2000) || (memory <= 512)

# Oil Change

The owner's manual for a car says to change the oil every three months or every 3000 miles.

boolean newOilNeeded = months >= 3 || miles >= 3000 ;

Here is an expression that shows when no oil change is necessary:

boolean oilOK = !( months >= 3 || miles >= 3000 );

Question 15:

Rewrite the last expression using one of De Morgan's rules. Do this in two steps. In the first step, don't change the relational expressions.

boolean oilOK =

Now further simplify by changing the relational expressions.

boolean oilOK =