In a race of one kilometre. A gives B a start of 100 metres and still wins by 20 seconds. But if A gives B a start of 25 seconds, B wins by 50 metres. The time taken by A to run kilometre is :
A. 17 sec
B. $$\frac{{500}}{{29}}{\text{sec}}$$
C. $$\frac{{1200}}{{29}}{\text{sec}}$$
D. $$\frac{{700}}{{29}}{\text{sec}}$$
Answer: Option B
Solution(By Examveda Team)
Let the time taken by A to run 1000 metres = x secondsTime taken by B to sun 900 metres = x + 20 seconds
Speed of A and B :
$$ = \frac{{1000}}{x},\frac{{900}}{{x + 20}}$$ respectively
According to the question,
$$\frac{{950}}{{\frac{{1000}}{x}}} - \frac{{1000}}{{\frac{{900}}{{x + 20}}}} = 25$$
(As B is the winner now)
$$\eqalign{ & \Rightarrow \frac{{950x}}{{1000}} - \frac{{1000\left( {x + 20} \right)}}{{900}} = 25 \cr & \Rightarrow \frac{{19x}}{{20}} - \frac{{10x + 200}}{9} = 25 \cr & \Rightarrow 171x - 200x - 4000 = 25 \times 20 \times 9 \cr & \Rightarrow 29x = 500 \cr & \Rightarrow x = \frac{{500}}{{29}}{\text{sec}} \cr} $$
Related Questions on Speed Time and Distance
A. 48 min.
B. 60 min.
C. 42 min.
D. 62 min.
E. 66 min.
A. 262.4 km
B. 260 km
C. 283.33 km
D. 275 km
E. None of these
A. 4 hours
B. 4 hours 30 min.
C. 4 hours 45 min.
D. 5 hours
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