Which of the following is not leap century year?

Solution: Determine whether each given year is a leap century year.

Rule: A year is a leap year if it is divisible by 4. However, century years (those ending with 00) are leap years only if they are divisible by 400.

• 2000: 2000 is a century year and 2000 ÷ 400 = 5, so it is divisible by 400 and is a leap century year.

• 1800: 1800 is a century year but 1800 ÷ 400 = 4.5, so it is not divisible by 400 and therefore is not a leap century year.

• 1200: 1200 is a century year and 1200 ÷ 400 = 3, so it is divisible by 400 and is a leap century year.

• 1600: 1600 is a century year and 1600 ÷ 400 = 4, so it is divisible by 400 and is a leap century year.

Conclusion: 1800 is not a leap century year because it is not divisible by 400.

Correct answer: 1800.