1. A man rows upstream 16 km and downstream 27 km talking 5 hours each time . What is the velocity of current?
a) 2 km/hr
b) 2.1 km/hr
c) 1.1 km/hr
d) 1.4 km/h
e) None of these
Sol. (c); Man’s rate upstream=16/5 km/hr
Man’s rate downstream=27/5 km/hr
Velocity of the current=1/2 (27/5-16/5) km/hr=1.1 km/hr
2. A boat moves downstream at the rate of one km in 7(1/2) minutes and upstream at the rate of 5 km an hour. What is the velocity of current?
a) 1.3 km/hr
b) 1.2 km/hr
c) 1.6 km/hr
d) 1.5 km/hr
e) None of these
Sol. (d); Rate downstream=(2/15 *60) km/hr=8 km/hr
Rate upstream=5 km/hr
Velocity of the current=1/2 (8-5) km/hr=1.5 km/hr
3. A person rows a kilometre down the stream 10 minutes and upstream in 30 minutes. Find velocity of the stream.
a) 1 km/hr
b) 2 km/hr
c) 3 km/hr
d) 4 km/hr
e) None of these
Sol. (b); Rate downstream=1/10 *60=6 km/hr
Rate upstream=1/30 *60=2 km/hr
Velocity of the stream=1/2 (6-2)=2 km/hr
4. A man can row three quarters of a km against the stream in 11 minutes 15 seconds ad return in 7 minutes 30 seconds. Find the speed of the man in still water and also the speed of the stream
a) 5 km/hr, 2 km/hr
b) 5 km/hr, 1 km/hr
c) 6 km/hr, 2 km/hr
d) 4 km/hr, 1 km/hr
e) None of these
Sol. (b); Rate upstream=3/4 * 4/45 * 60=4 km/hr
Rate downstream=3/4 * 2/15 * 60=6 km/hr
Speed of the man in still water (6+4)1/2=5 km/hr
Speed of the stream=(6-4) ½=1 km/hr
5. A boat's man goes 48 km downstream in 8 hours ad return back in 12 hours. Find the speed of the boat in still water and the rate of the stream.
a) 5 km/hr, 1 km/hr
b) 10 km/hr, 2 km/hr
c) 6 km/hr, 1.5 km/hr
d) can't be determine
e) None of these
Sol. (a); Rate downstream=48/8 =6 km/hr
Rate upstream= 48/12 = 4 km/hr
6. A boat moves with a speed of 11 km per hour ad along the stream and 7 km per hour against the stream. The rate of the stream is ______km/hr.
a) 1 km/hr
b) 1.5 km/hr
c) 2 km/hr
d) 2.5 km/hr
e) None of these
Sol. (c); 1/2 (11-7)=2 km/hr
7. A man rows upstream 11 km ad downstream 26 km tak-ing 5 hours each time. The velocity of the current is _______ km/hr.
a) 1 km/hr
b) 1.3 km/hr
c) 1.5 km/hr
d) 2.5 km/hr
e) None of these
Sol. (c); U=11/5, D=26/5
Y=1/2 (26/5 – 11/50) =1.5 km/hr
8. A boat moves downstream at the rate of 1 km in 6 minutes and upstream at the rate of 1 km in 10 minutes. The speed of the current is
a) 2 km/hr
b) 1 km/hr
c) 1.5 km/hr
d) 2.5 km/hr
e) None of these
Sol. (a); D=60/6 =10 km/hr
U=60/10=6 km/hr
Y= 1/2 (10-6)=2 km/hr
9 The speed of a boat downstream is 15 km/hr and the speed of the stream is 1.5 km/hr. The speed of the boat upstream is
a) 13.5 km/hr
b) 16.5 km/hr
c) 12 km/hr
d) 8.25 km/hr
e) None of these
Sol. (c); D=15 km/hr
Y=1.5
X=15-1.5=13.5
U=13.5-1.5=12 km/hr
10 If a man's rate with the current is 12 km/hr and the rate of current is 1.5 km/hr, then the man's rate against the current is
a) 9 km/hr
b) 6.75 km/hr
c) 5.25 km/hr
d) 7.5 km/hr
e) None of these
Sol. (a); D=12 km/hr
X=12-1.5=10.5
V=10.5-1.5=9 km/hr
