A shopkeeper has 13 washing machines out of which 5 are defective. A customer buys 3 washing machine. What is the probability that exactly one machine is defective?
(a) 1/20 (b) 1/5 (c) 70/143 (d) 35/143
Supriya runs a marathon race in 50 minutes at an average speed of 48 km/hrs . in order to set a national record she needs to win the race in 40 minutes considering that her speed remains constant at what minimum speed should she run to set the record?