Math Kangaroo

Math Kangaroo is a popular math contest. There are 24 questions in the test. Each question has point value. 1/3 of questions are 3 points each; 1/3 are 4 points each, 1/3 are 5 points each. The sum of earned points is the student's final score. Leo and five other kids join the contest. The median and mean of their scores are both 90. If they all have different scores, what's the lowest possible score among them?

Oreo Cookies

After Dr. Hong, Leo and William complete a basketball workout, they open a pack of Oreo cookies to share among themselves. If there are 12 cookies in the pack, and if each person gets at least one cookie, how many different ways are there to distribute the cookies? (They do not split a cookie.) 

Tangent Circles

Points A, B and C are the pairwise points of tangency of three externally tangent circles of radius 1. What's the area surrounded by the arcs AB, BC and CA? 

House Cleaning

Leo's mom asks Dr. Hong, Leo and Angela to clean up the house. If Dr. Hong and Leo work together, they can complete the task in 1.5 hours. If Dr. Hong and Angela work together, it would take them 1.75 hours. If Leo and Angela work together, it would take them 4.2 hours. If all three of them work together, how long does it take to clean up the house?  

Favorite Math Subjects

30 CMM students get together and discuss their favorite math subjects. 23 of them like geometry; 29 of them like algebra; 19 of them like probability. At most how many students like all three subjects?

Logo Shot

In the expression LOGO + SHOT = HARD, each letter represents a single digit number from 0 to 9. Different letters represent different numbers. L, S and H cannot be zero. What's the difference between the largest and smallest values of HARD?