3. In a relay race of 4 × 100 meters (4 sprinters each running 100 meters successively), the speed of the four athletes is 8 m/s, 6 m/s, 8 m/s and 12 m/s. Find the time in which the team completes the 400 meter race.

4. While going to office, I am in a hurry and hence I travel at 60 kmph but while coming back from office I drive at a more leisurely speed of 40 kmph. If I take a total of 30 minutes for both the way, find the distance to my office.

5. I cover a total of 300 km in 8 hours, partly at a speed of 30 kmph and partly at a speed of 50 kmph. For what time was I traveling at a speed of 30 kmph?

6. Find the ratio of the time taken to cover two distances in the ratio 4 : 5 at speeds in the ratio 4 : 3 respectively