The mean of 100 observations was calculated as 40. It was found later on that one of the observations was misread as 83 instead of 53. The correct mean is:
Three clocks are designed to alarm in every hour, two hours and three hours respectively. If they all alrmed together three hours before, then after how many hours will they next alarm together?
Two equal circles intersect so that their centres, and the points at which they intersect form a square of side 1 cm. The area (in sq.cm) of the portion that is common to the circles is