12. A train running at 7/11 of its own speed reached a place in 22 hrs.How much time could be save if the train would have run at its own speed?

A. 7 hrs B. 8 hrs C. 14 hrs D. 16 hrs

Answer Answer: Option B Explanation: New speed 7/11 of usual speed
New time =11/7 of usual time
So 11/7 of usual time = 22 hrs = usual time = (22*7/11) = 14 hrs
Hence time saved = (22-14) = 8hrs

13. A car traveling with 5/7 of its actual speed covers 42 km in 1 hour 40 minutes 48 sec.Find the actual speed of the car.

A. 17 6/7 km/hr B. 25 km/hr C. 30 km/hr D. 35 km/hr

Answer Answer: Option D Explanation: Time taken = 1hr 40 minutes 48 seconds = 1hr 44/5 minutes = 1 51/75 hrs = 126/75 hrs
Let the actual speed be x km/hr
Then 5/7x * 126/75 = 42 or x = (42*7*75/5*126) = 35 km/hr

14. Mary jogs 9 km at a speed of 6 km/hr. At what speed would see need to jog during the next 1.5 hrs to have an average of 9 km/hr for the entire jogging session?

A. 9 km/hr B. 10 km/hr C. 12 km/hr D. 14 km/hr

Answer Answer: Option C Explanation: Let speed of jogging be X km/hr
Total time take = (9/6 hrs + 1.5 hrs) = 3 hrs
Total distance covered = ( 9+1.5 + x) km
Hence = 9/1.5 x / 3 = 9 = 9 + 1.5 x = 27 = 3/2 x = 18 = x= (18*2/3) = 12 km/hr.

15. A car travels the first one-third of a certain distance with a speed of 10 km/hr, the next 1/3rd distance with a speed of 20 km/hr, and the last 1/3rd distance with a speed 60 km/hr. the average speed of the car for the whole journey is?

A. 18 km/hr B. 24 km/hr C. 30 km/hr D. 36 km/hr

Answer Answer: Option A Explanation: Le the whole distance traveled be x km/hr and the average speed of the car for the whole journey be y km/hr.
Then,( x /3) / 10 + (x/3) / 20 + (x/3) / 60 = x/y = x/30+ x/60+x/180 = x/y
= 1/18 y = 1 = y = 18 km/hr