A man goes upstream for a distance of 10 kms in 5 hours. Another man goes downstream the same distance of 10 kms in 3 hours. what is the difference in speeds of two men if the river speed is 0.5 km/hr
since distance = speed*time, if the still-water speeds of the men are a and b,
(a-.5)(5) = 10
(b+.5)(3) = 10
5a - 5/2 = 10
3b + 3/2 = 10
b-a = (10 - 3/2)/3 - (10+5/2)/5 = 1/3
Sir, I am also getting this as the answer. but the options given are :-
a). 2.45
b). 2.3
c). 1.33
d). 1.56
upstream speed =Distance/time
=10/5=2 kmph
downstream speed of =10/3=3.33kmph
difference =3.33-2=1.33
To find the difference in speeds of the two men, we first need to calculate the speed of each man relative to the water.
Let's assume the speed of the first man (going upstream) is 'x' km/hr. Since he is going against the current, his effective speed will be reduced by the rate of the river's flow, which is 0.5 km/hr. Therefore, his actual speed against the stream will be (x - 0.5) km/hr.
Using the formula: speed = distance/time, we can calculate the actual speeds of the two men:
Speed of the first man (going upstream) = 10 km / 5 hours = 2 km/hr
Actual Speed of the first man (against the current) = 2 km/hr - 0.5 km/hr = 1.5 km/hr
Speed of the second man (going downstream) = 10 km / 3 hours = 3.33 km/hr
Now, we can calculate the difference in speeds:
Difference in speeds = Speed of the second man - Actual Speed of the first man
= 3.33 km/hr - 1.5 km/hr
= 1.83 km/hr
Therefore, the difference in speeds between the two men is 1.83 km/hr.