Hoang's roll number is a two digit number. His friend Annie's roll number has the same digits as Hoang's roll number, but with digits interchanged. If they add their roll number, and divide the sum by 11. Find the remainder of this division.
Can not be determined without knowing the roll number
It is Trinh's birthday today and she distributed toffees to her classmates. The toffees were in a bag as shown below. Trinh's puts her hand in the bag and takes out a toffee without looking. What is the probability that she picked out a striped toffee?
During a day, the hour hand and the minute hand of a clock forms a right angle, at multiple times. For example, the two hands form a right angle at 9 am. How many times during a day (24 hours) will the two hands form a right angle?