While many countries celebrate Lunar New Year, the specific date and set of 12 zodiac animals varies. The problems below reflect the date and animals used in China, and Lunar New Year is referred to as “Chinese New Year” to reflect this distinction.
While there were many problems written and solved for MATHCOUNTS in 2020, below is a selection of some of the best of the year!
As November (the 11th month) gets underway, it’s the perfect time to focus on 11. Eleven is the fourth prime number, and there is a fun divisibility rule for 11. For any integer, insert alternating “–” and “+” signs between the consecutive pairs of digits, starting with a “–” sign between the left-most pair of digits. For example, for the number 91,828 we would have 9 – 1 + 8 – 2 + 8.
Friends Megan and Heather go to different schools. Megan has math class during first period on each of the 180 days she goes to school. She will be in math class a total of 8640 minutes this year. Heather’s school year also has 180 days, but her math class only meets every other day, so her class periods are longer. (One day she’ll have math class, and then the next day she won’t.) If Megan and Heather end up with the same number of minutes of math class e
Whole numbers are said to be abundant, deficient, or perfect. A whole number is abundant if the sum of its proper divisors is greater than the whole number.
The following problem of the week was submitted by Tim Ramsey of the Singapore American School in 1999.
During the month of February, the 2020 Chapter Competitions took place across the country. Let’s look back at a few of the problems our competitors encountered.