21. Mac travels from A to B a distance of 250 miles in 5 1/2 hours. He returns to A in 4 hours 30 minutes. his average speed is?

A. 44 mph B. 46 mph C. 48 mph D. 50 mph

Answer Answer: Option D Explanation: Speed from A to B =(250*2/11) mph = (500/11) mph.
Speed from B to A =(250*2/9) mph = (500/9) mph.
Therefore average speed =(2*500/11*500/9/500/11+500/9) mph = (500000/4500+5500)mph = 50 mph

22. A car drive travels from the plains to the hill station, which are 200 km apart at an average speed of 40 km/hr. In the return the trip, he covers the same distance at an average speed of 20 km/hr. the average speed of the car over the entire distance of 400 km is?

A. 25 km/hr B. 26.67 km/hr C. 28.56 km/hr D. 30 km/hr

Answer Answer: Option B Explanation: Average speed = (2*40*20/ 40+60) km/hr = 80/3 km/hr = 26.67 km/hr.

23. A person travels from P to Q at a speed of 40 kilometer per hour and returns by increasing his speed by 50%. What is his average speed for both the trips?

A. 36 kilometer per hour B. 45 kilometer per hour C. 48 kilometer per hour D. 50 kilometer per hour

Answer Answer: Option C Explanation: Speed on return trip = 150% of 40 = 60 kilometer per hour.
therefore average speed = (2*40*60/40+60) km/hr = (4800/100)km/hr = 48 km/hr.

24. A is faster than B. A and B each walk 24 km.The sum of their speeds is 7 km/hr and the sum of times taken by them is 14 hours.Then A's speed is equal to:

A. 3 km/hr B. 4 km/hr C. 5 km/hr D. 7 km/hr

Answer Answer: Option B Explanation: Let A's speed = x km/hr. Then B's speed =(7-x) km/hr
24/x + 24/(7-x) = 14
24 (7-x) +24x = 14x (7-x)
= 14 x^2 - 98x + 168 =0
x^2 -7x +12= 0
(x-3) (x-4) = 0
x=3 or x= 4
Since A is faster than B, so A's speed = 4km/hr and B's speed = 3km/hr.

25. A farmer traveled a distance of 61km in9 hrs. He traveled partly on foot @ 4 km/hr and partly on bicycle @ 9 km/hr.The distance traveled on foot is:

A. 14 km B. 15 km C. 16 km D. 17 km

Answer Answer: Option C Explanation: Let the distance traveled on foot be x km
then distance traveled on bicycle =(61-x)km
so x/4 + (61-x)/9-9 =9x+ 4(61-x)
= 9*36 = 5x =80 = x=16km