A cylindrical container of three rubber balls has a height of 18 cm in the diameter of 6 cm each ball in the container has a radius of 3 cm find the amount of space in the container that is not occupied by rubber balls round your answer to the nearest whole number

Lizette is training for a marathon. at 7: 00 she left her house and ran until 8: 30, then she walked until 11: 30. she covered a total distance of 18 miles. her running speed was six miles per hour faster than her walking speed. find her running and walking speeds in miles per hour.