To calculate $18 \mod 5$:

1. Divide 18 by 5: $18 \div 5 = 3 \text{ (quotient)}$

2. Multiply the quotient by the divisor: $3 \times 5 = 15$

3. Subtract this result from 18: $18 - 15 = 3$

Thus, $18 \mod 5 = 3$.

Would you like more details on modular arithmetic?

Here are 5 related questions:

1. What is $27 \mod 4$?
2. How does modular arithmetic apply to clock time calculations?
3. Can you explain the relationship between division and the modulus operation?
4. What is the result of $45 \mod 6$?
5. How can modular arithmetic be used in cryptography?

Tip: In modular arithmetic, the result is always a non-negative integer less than the divisor.