The sum of the reciprocals of two numbers is 1/4. How many times their sum is their product?

In the figure, ABC is an isosceles triangle (AB=AC) and BD is the bisector of angle B and BD=BC. How much is angle C?

Each side of a square is 10 meters long. A rectangle of the same perimeter as this has sides in the ratio 2:3. What is the area of the rectangle in square meters?

2.5 bottles of the same size are filled with 1.5 litres of water. How many millilitres does each bottle contain?

The empty squares below are to be filled by writing numbers: 1, blank, blank, blank, blank, 6 (six squares in a row). The sum of the numbers in any three consecutive squares must be 10. What number should be written on the second square?