Required distance = (150 - 20) m = 130 m
Raman covers 1 km in 8 min
and suman cover 1 km in 10 min.
If they starts together, then distance covered by suman in 8 min
= (1000/10) x 8 = 800 m
? Raman will beat suman by (1000 - 800 ) m = 200 m
Suppose that the man takes H hours to cover 4 km downstream and H house to cover 3 km upstream.
Then, 48H/4 + 48H/3 = 14
? H = 1/2
? Rate upstream = 3/(1/2)= 6 km/hr
and rate downstream = 4/(1/2) = 8 km/hr
? Rate of the stream = (8 - 6)/2 = 1 km/hr .
? [(9 + 6)/(9 - 6)] x v = 12
? v = 2.4 km/hr
Upstream distance = (4 - 2) x 9 = 18 km
? Required time = 18/(4 + 2) = 3 hrs.
Let the speed of a boat and stream be U and V km/h
? Speed of boat along stream = (U + V) km/h
and speed of boat against stream = (U - V) km/h
According to the question,
25/(U - V) + 39/(U + V) = 8 ....(i)
and 35/(U - V) + 52/(U + V ) = 11 ..(ii)
On multiplying Eq. (i) by 4 and Eq. (ii) by 3, then subtract Eq. (ii) from Eq, we get
100/(U - V) - 105/(U - V) = -1
? 5/(U - V) = 1
? U - V = 5 ...(iii)
On substituting the value of (U - V) = 5 in Eq. (i) we get
25/5 + 39/(U + V) = 8
? 39/(U + V) = 8 - 5
? U + V = 39/3
? U + V = 13 ....(iv)
On solving Eqs. (iii) and (iv), we get
U = 9 and V = 4
Hence, speed of stream = 4 km/h
Required length = (175 + 25)m = 200 m
Start given by A to B = (800 - 725)m = 75 m
Score of A = 100 points
Score of B = 65 points
? A can give (100 - 65 ) = 35 points to B.
Clearly, B covers 18 m in 9 s.
? B's time over the course = 9/18 x 1000 = 500 s
? A' s time over the course = (500 - 9) = 491 s
Clearly, Y covers 140 m in 14 s
? Y' s time over the course = (14/140) x 1000 = 100 s
? X' s time over the course = 100 - 14 = 86 s
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