Ratio of speed of boat in down stream and speed of stream is 9:1, if speed of current is 3 km per  hr, then find distance travelled(in km) upstream in 5 hours.

A person has to cover a distance of 160 km in 15 hours. If he covers $${4\over 5}$$ of the distance in $${2\over 3}$$  of the time, then what should be his speed (in km/h) to cover the remaining distance in the remaining time?

A bullet travels at 750 m/s. How long will it take to travel 1 km?

Sound travels 330 meters in one second. When the sound is heard 10 seconds after the lightning flashes, then at what distance will the cloud be?

A man can row at 7 km/hour in still water. He finds that it takes twice the time to row upstream than the time to row downstream. The speed of the stream is

Ravi drove for 4 hours at a speed of 70 miles per hour and for 2 hours at 40 miles per hour. What was his average speed (in miles per hour) for the whole journey?

A car runs first 275 km at an average speed of 50 km/h and the next 315 km at an average speed of 70 km/h. What is the average speed (in km/h) for the entire journey?

Rajesh covers the distance by car driving at 60 kmph and returns back to the starting point riding on a scooter at 45 kmph. What is his average speed?