Question

6.
1
7.
The speed of a boat in still water is 9
km/hr and the speed of the stream
is 2.5 km/hr. How much time will
the boat take to go 9.1 km against
the stream?
(1) 1 hr 20 min. (2) 1 hr.24 min.
(3) 1 hr.30 min. (4) 2 hrs.24 min.
(5) None of these
A swimmer swims a distance of 36
km in 6 hours downstream and a
distance of 40 km upstream in 8
hours. What is his speed in still
water?
(1) 5.5 km/hr (2) 6 km/hr
(3) 7 km/hr
(4) 11km/hr
(5) None of these
1​

Answer 1

Answer:

option 2

Step-by-step explanation:

Speed of boat in still water (Sb) = 9 km/hr, Speed of stream (Sc) = 2.5 km/hr, Distance against the stream = 9.1 km

Speed of boat upstream = speed of boat - the speed of the stream

The speed of upstream = 9 - 2.5 = 6.5 km/hr  

Now, time= Distance/speed  

Time = 9.1/6.5, or 7/5 Or, time = 1+[2/5] Or, 1 hr + (2/5)*60 = 1 hr + 24 minutes

or

Time = 9.1/6.5 = 1.4hr

ie, 1.4hr*60=84min

84min = 60 min + 24 min = 1hr 24 min