There are 3 members in a family. The average age of the father and mother is 40 years. The average age of the father, mother and daughter is 30 years. Find the age (in years) of the daughter.
A policeman noticed a thief from 300 m. The thief started running and the policeman was chasing him. The thief and the policeman ran at the speeds of 8 km/h and 9 km/h, respectively. What was the distance between them after 3 minutes?