Each of the four cards has a letter on one side and a number on the other. Raza claims every vowel has an even number on its reverse. What is the fewest cards Sara must turn to check this?
Two equal-length trains travel oppositely at 100 and 120 km/h. A passenger on the second sees the first pass completely in 6 seconds. How long does a passenger on the first see the second pass?
Two pendants have the same material, thickness and weight. One is an annulus of concentric radii 6 cm and 4 cm, the other a solid disk. Find its radius.
Every nine-digit integer using digits 1, …, 9 once is put on a separate sheet in a box. How many sheets guarantee at least two numbers with the same first digit?
A circular traffic sign has radius 20 cm. Each dark piece is a quarter-circle; the four dark pieces together equal the light area. What is the radius of a dark quarter-circle?
Sixteen volleyball teams each play every other once. A win gives 1 point, a loss 0, no draws. The final scores form an arithmetic sequence. How many points does the last team have?