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21
If a person walks at 14 km/hr instead of 10 km/hr, he would have walked 20 km more. The actual distance travelled by him is:
Discuss
Answer & Solution
Answer: Option A
Solution:
$$\eqalign{ & {\text{Let}}\,{\text{the}}\,{\text{actual}}\,{\text{distance}}\,{\text{travelled}}\,{\text{be}}\,x\,km \cr & {\text{Then}},\,\frac{x}{{10}} = \frac{{x + 20}}{{14}} \cr & \Rightarrow 14x = 10x + 200 \cr & \Rightarrow 4x = 200 \cr & \Rightarrow x = 50\,km \cr} $$
22
A train can travel 50% faster than a car. Both start from point A at the same time and reach point B 75 kms away from A at the same time. On the way, however, the train lost about 12.5 minutes while stopping at the stations. The speed of the car is:
Discuss
Answer & Solution
Answer: Option C
Solution:
$$\eqalign{ & {\text{Let}}\,{\text{speed}}\,{\text{of}}\,{\text{the}}\,{\text{car}}\,{\text{be}}\,x\,kmph \cr & {\text{Then,}}\,{\text{speed}}\,{\text{of}}\,{\text{the}}\,{\text{train}} \cr & = \frac{{150}}{{100}}x = {\frac{3}{2}x} \,kmph \cr & \therefore \frac{{75}}{x} - \frac{{75}}{{\left( {3/2} \right)x}} = \frac{{125}}{{10 \times 60}} \cr & \Rightarrow \frac{{75}}{x} - \frac{{50}}{x} = \frac{5}{{24}} \cr & \Rightarrow x = {\frac{{25 \times 24}}{5}} \cr & \Rightarrow x = 120\,kmph \cr} $$
23
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?
Discuss
Answer & Solution
Answer: Option B
Solution:
$$\eqalign{ & {\text{Due}}\,{\text{to}}\,{\text{stoppages,}}\,{\text{it}}\,{\text{covers}}\,{\text{9}}\,{\text{km}}\,{\text{less}} \cr & {\text{Time}}\,{\text{taken}}\,{\text{to}}\,{\text{cover}}\,{\text{9}}\,{\text{km}} \cr & = \left( {\frac{9}{{54}} \times 60} \right)\min \cr & = 10\ \text{minutes} \cr} $$
24
In a flight of 600 km, an aircraft was slowed down due to bad weather. Its average speed for the trip was reduced by 200 km/hr and the time of flight increased by 30 minutes. The duration of the flight is:
Discuss
Answer & Solution
Answer: Option A
Solution:
$$\eqalign{ & {\text{Let}}\,{\text{the}}\,{\text{duration}}\,{\text{of}}\,{\text{the}}\,{\text{flight}}\,{\text{be}}\,x\,{\text{hours}} \cr & {\text{Then}},\frac{{600}}{x} - \frac{{600}}{{x + \left( {1/2} \right)}} = 200 \cr & \Rightarrow \frac{{600}}{x} - \frac{{1200}}{{2x + 1}} = 200 \cr & \Rightarrow x\left( {2x + 1} \right) = 3 \cr & \Rightarrow 2{x^2} + x - 3 = 0 \cr & \Rightarrow (2x + 3)(x - 1) = 0 \cr & \Rightarrow x = 1\,\text{hour} \cr} $$
25
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.
Discuss
Answer & Solution
Answer: Option B
Solution:
$$\eqalign{ & \frac{{\left( {1/2} \right)x}}{{21}} + \frac{{\left( {1/2} \right)x}}{{24}} = 10 \cr & \Rightarrow \frac{x}{{21}} + \frac{x}{{24}} = 20 \cr & \Rightarrow 15x = 168 \times 20 \cr & \Rightarrow x = {\frac{{168 \times 20}}{{15}}} \cr & \Rightarrow x = 224\,km \cr} $$
26
The ratio between the speeds of two trains is 7 : 8. If the second train runs 400 km in 4 hours, then the speed of the first train is:
Discuss
Answer & Solution
Answer: Option D
Solution:
$$\eqalign{ & {\text{Let}}\,{\text{the}}\,{\text{speed}}\,{\text{of}}\,{\text{two}}\,{\text{trains}}\,{\text{be}}\,7x\,{\text{and}}\,8x\,{\text{km/hr}} \cr & {\text{Then}},\,8x = {\frac{{400}}{4}} = 100 \cr & \Rightarrow x = {\frac{{100}}{8}} = 12.5 \cr & \therefore {\text{Speed}}\,{\text{of}}\,{\text{first}}\,{\text{train}} \cr & = \left( {7 \times 12.5} \right){\text{km/hr}} \cr & = 87.5\,{\text{km/hr}} \cr} $$
27
A man on tour travels first 160 km at 64 km/hr and the next 160 km at 80 km/hr. The average speed for the first 320 km of the tour is:
Discuss
Answer & Solution
Answer: Option C
Solution:
$$\eqalign{ & {\text{Total}}\,{\text{time}}\,{\text{taken}} \cr & = \left( {\frac{{160}}{{64}} + \frac{{160}}{{80}}} \right)hrs \cr & = \frac{9}{2}\,hrs \cr & \therefore {\text{Average}}\,{\text{speed}} \cr & = \left( {320 \times \frac{2}{9}} \right)\,{\text{km/hr}} \cr & = 71.11\,{\text{km/hr}} \cr} $$
28
A car travelling with $$\frac{5}{7}$$ of its actual speed covers 42 km in 1 hour 40 minute 48 second. Find the actual speed of the car.
Discuss
Answer & Solution
Answer: Option D
Solution:
$$\eqalign{ & {\text{Time}}\,{\text{taken = 1}}\,{\text{hr}}\,{\text{40}}\,{\text{min}}\,{\text{48}}\,{\text{sec}} \cr & = 1\,{\text{hr}}\,40\frac{4}{5}\,{\text{min}} = 1\frac{{51}}{{75}}\,hrs = \frac{{126}}{{75}}\,hrs \cr & {\text{Let}}\,{\text{the}}\,{\text{actual}}\,{\text{speed}}\,{\text{be}}\,x\,{\text{km/hr}} \cr & {\text{Then}},\,\frac{5}{7}x \times \frac{{126}}{{75}} = 42 \cr & \Rightarrow x = {\frac{{42 \times 7 \times 75}}{{5 \times 126}}} \cr & \Rightarrow x = 35\,{\text{km/hr}} \cr} $$
29
In covering a distance of 30 km, Abhay takes 2 hours more than Sameer. If Abhay doubles his speed, then he would take 1 hour less than Sameer. Abhay's speed is:
Discuss
Answer & Solution
Answer: Option A
Solution:
$$\eqalign{ & {\text{Let}}\,{\text{Abhay's}}\,{\text{speed}}\,{\text{be}}\,{\text{x}}\,{\text{km/hr}} \cr & {\text{Then}},\,\frac{{30}}{x} - \frac{{30}}{{2x}} = 3 \cr & \Rightarrow 6x = 30 \cr & \Rightarrow x = 5\,{\text{km/hr}} \cr} $$
30
Robert is travelling on his cycle and has calculated to reach point A at 2 P.M. if he travels at 10 kmph, he will reach there at 12 noon if he travels at 15 kmph. At what speed must he travel to reach A at 1 P.M.?
Discuss
Answer & Solution
Answer: Option C
Solution:
$$\eqalign{ & {\text{Let}}\,{\text{the}}\,{\text{distance}}\,{\text{travelled}}\,{\text{by}}\,x\,{\text{km}} \cr & {\text{Then}},\,\frac{x}{{10}} - \frac{x}{{15}} = 2 \cr & \Rightarrow 3x - 2x = 60 \cr & \Rightarrow x = 60\,km \cr & {\text{Time}}\,{\text{taken}}\,{\text{to}}\,{\text{travel}}\,60\,km\,{\text{at}}\,10\,{\text{km/hr}} \cr & = {\frac{{60}}{{10}}} \,hrs = 6\,hrs \cr & {\text{So,}}\,{\text{Robert}}\,{\text{started}}\,{\text{6}}\,{\text{hours}}\,{\text{before}}\,2\,P.M.\,i.e.,\,at\,A.M. \cr & \therefore {\text{Required}}\,{\text{speed}} \cr & = {\frac{{60}}{5}} \,kmph = 12\,kmph \cr} $$