A and B start from the same point and in the same direction at 7 am to walk around a rectangular field 400 m × 300 m. A and B walk at the rate of 3 km/hr and 2.5 km/hr respectively. How many times shall they cross each other if they continue to walk till 12.30 pm ?
A. Not even once
B. Once
C. Twice
D. Thrice
Answer: Option B
Solution(By Examveda Team)
Perimeter of the field= 2(400 + 300) m
= 1400 m
= 1.4 km
Since A and B move in the same direction, so they will first meet each other when there is a difference of one round i.e., 1.4 km between the two.
Relative speed of A and B = (3 - 2.5) km = 0.5 km/hr
Time take to cover 1.4 km at this speed :
$$\eqalign{ & = \left( {\frac{{1.4}}{{0.5}}} \right){\text{ hr}} \cr & = 2\frac{4}{5}{\text{ hr}} \cr & = 2{\text{ hr 48 min}} \cr} $$
So, they shall first cross each other at 9.48 am
And again 2 hr 48 min after 9.48 am i,e., 12.36 pm
Thus, till 12.30 pm they will cross each other once.
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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