time , distance and speed
1. A man can row 30 km upstream and 44 km downstream in 10 hours. It is also known that he can row 40 km upstream and 55 km downstream in 13 hours. Find the speed of man in still water?
A. 4km/hr B. 6 km/hr
C. 8 km/hr D. 12 km/hr
2. between 5 a.m and 5 p.m of a particular day for how many times are the minute and hour hand together?
A. 11 B.22
C.33 D.44
3. At what time are the hands of clock together between 2 and 3 pm?
A. 2/11 hrs past 2 p.m. B.2/9 hrs past 2 p.m.
C. 2:10 p.m. D.none of these
At 2 PM the distance between Hour hand and Minute hand = 60 degree
in 1 minute, minute hand crosses 6 degree and hour hand crosses 1/2 degree
Let they meet after t minute
then (t/2 + 60) degree = 6t degree
=>6t - t/2 = 11t/2 = 60
=> t = 120/11 min = 2/11 hr
so they 'll meet at 2/11 hrs past 2 p.m. (ans a)
thanks
the answers provided by u r correct.
two persons r1 and r2 start simultaneously from a and b and walk towards each other.they meet after (1/2)hour and continue to walk towards their destinatiions if r1 reaches 25 minutes after r2 reached his destination find the ratio speeds of r1 and r2.
Let
the speed of r1 & r2 are x & y.
Time taken by r2 = t
then time taken by r1 = t+25
then
1/2 x + 1/2 y = total distance between a & b
1/2(x+y)=yt => t =1/2(x-y) -------------------------------eq 1
1/2(x+y)=x(t+25)=> t+25 = 1/2 +1/2(y/x)
=> t = 1/2 +1/2(y/x)- 25 ------------------eq 2
Let u = Velocity of man in still water
v = Velocity of stream
Then
10 = 30/(u-v) + 44/(u+v)
13 = 40/(u-v) + 55/(u+v)
Solve the above two eqn to get u