An inspector is 228 meter behind the thief. The inspector runs 42 meters and the thief runs 30 meters in a minute. In what time will the inspector catch the thief?
(a) 19 minutes
(b) 20 minutes
(c) 18 minutes
(d) 21 minutes
(e) None of these
Answer: (a)
Inspector s 228 meter behind the thief and now after some x distance he will catch the thief. So,
\(\displaystyle \frac{x}{{30}}=\frac{{228+x}}{{42}}\) we will get x = 570m
So time taken by inspector to catch the thief = \(\displaystyle \frac{{(228+570)}}{{42}}=19\min utes\)
Ashok can row upstream at 8 kmph and downstream at 12 kmph.What is the speed of the stream?
(a) 6km/hr
(b) 3km/h
(c) 2 km/hr
(d) 4km/hr
(e) 4.5km/hr
Answer: (c)
If the speed downstream is a kmph and the speed upstream is b kmph then
Speed of the stream = \(\displaystyle \frac{1}{2}(a-b)kmph\)
Explanation:
Speed downstream a = 12 kmph
Speed upstream b = 8 kmph
Speed of the stream = \(\displaystyle \frac{1}{2}(a-b)=\frac{1}{2}(12-8)=\frac{4}{2}=2kmph\)
Speed of the stream = 2 kmph
Ashwin has to travel from one point to another point in a certain time. Travelling at a speed of 6kmph he reaches 40m late and travelling at a speed of 8kmph he reaches 12 m earlier. What is the distance between this two points?
D = \(\displaystyle \frac{{52\times 48}}{{60\times 2}}=20.8=21km\)
Two cities A and B are at a distance of 60 km from each other. Two persons P and Q start from First city at a speed of 10km/hr and 5km/hr respectively. P reached the second city B and returns back and meets Q at Y. Find the distance between A and Y.
(a) 30 km
(b) 40 km
(c) 50 km
(d) 55 km
(e) 53 Km
Answer: (b)
Time taken by P to reach city B is 6hr. In 6 hr, distance covered by Q is 30km. Now at some x distance they will meet.
So \(\displaystyle \frac{x}{5}=\frac{{(30-x)}}{{10}};x=10\)
So distance between A and Y is 30+10 =40 km
A man walking at the rate of 5 km/hr. crosses a bridge in 15 minutes. The length of the bridge (in metres) is :
