Quantitative aptitude- time and speed

1. A man takes 5 hours 45 min in walking to a certain place and riding back. He would have gained 2 hours by riding both ways. The time he would take to walk both ways is
A. 11 hrs	B. 8 hrs 45 min
C. 7 hrs 45 min	D. 9 hrs 20 min

Here is the answer and explanation

Answer : Option C

Explanation :

Given that the time needed for walking one way and riding back=5.45

 time taken for riding both ways = 5.45-2.00 = 3.45

 time needed for riding one way = 1.725

time needed for walking one way  = 5.450-1.725 = 3.725

time needed for walking both way = 3.725*2 = 7 hrs 45 min

2. A person crosses a 600 m long street in 5 minutes. What is his speed in km per hour?
A. 8.2                                        B. 4.2 C. 6.1 D. 7.2
Answer : Option D Explanation :  Answer : Option D Explanation : distance = 600 meter time = 5 minutes = 5 x 60 seconds = 300 seconds Speed = distancetime=600300=2m/s=2×185 km/hr=365 km/hr=7.2 km/hr 3. Excluding stoppages, the speed of a bus is 54 kmph and including stoppages, it is 45 kmph. For how many minutes does the bus stop per hour? A. 12 B. 11 C. 10 D. 9 Here is the answer and explanation Answer : Option C Explanation : speed of the bus excluding stoppages = 54 kmph speed of the bus including stoppages = 45 kmph Loss in speed when including stoppages = 54 - 45 = 9kmph => In 1 hour, bus covers 9 km less due to stoppages Hence, time that the bus stop per hour = time taken to cover 9 km =distancespeed=954 hour=16 hour = 606 min=10 min 4. A man complete a journey in 10 hours. He travels first half of the journey at the rate of 21 km/hr and second half at the rate of 24 km/hr. Find the total journey in km. A. 121 km B. 242 km C. 224 km D. 112 km Answer : Option C Explanation : distance = speed x time Let time taken to travel the first half = x hr then time taken to travel the second half = (10 - x) hr Distance covered in the the first half = 21x Distance covered in the the second half = 24(10 - x) But distance covered in the the first half = Distance covered in the the second half => 21x = 24(10 - x) => 21x = 240 - 24x => 45x = 240 => 9x = 48 => 3x = 16 ⇒x=163Hence Distance covered in the the first half = 21x=21×163=7×16=112 kmTotal distance = 2×112=224 km 5. A car traveling with 5/7 of its actual speed covers 42 km in 1 hr 40 min 48 sec. What is the actual speed of the car? A. 30 km/hr B. 35 km/hr C. 25 km/hr D. 40 km/hr Answer : Option B Explanation : Time = 1 hr 40 min 48 sec = 1hr +4060hr+483600hr=1+23+175=12675hrdistance = 42 kmspeed=distancetime=42(12675)=42×75126⇒57 of the actual speed = 42×75126⇒actual speed = 42×75126×75=42×1518=7×153=7×5=35 km/hr