Two smaller circles touch a large circle internally and pass through the center O of the larger circle. If the diameter of the bigger circle is 28 cm, thenwhat is the area of the bigger circle which is not enclosed by the two smaller circles (in sq.cm)?
It takes eight hours for a 600 km journey, if 120 km is done by train and the rest by car. It takes 20 minutes more, if 200 km is done by train and the rest by car. The ratio of the speed of the train to that of the car is: