1. Speed, Time and Distance Relation:
Speed = Distance/Time
Time = Distance/Speed
Distance = (Speed x Time)
2. km/hr to m/sec conversion:
X km/hr = X x 5/18 m/sec.
3. m/sec to km/hr conversion:
X m/sec = X x 18/5 km/hr.
4. If the ratio of the speeds of A and B is a : b, then the ratio of the
the times taken by then to cover the same distance is 1/a : 1/b or b : a.
5. Suppose a man covers a certain distance at x km/hr and an equal distance at y km/hr. Then, the average speed during the whole journey is 2xy/x+y km/hr.
1. 

The distance between P and Q = 3 x 60 = 180 km
2. 

From 9:00 am to 10:00 am , A travels for 1 hour i.e. 60 km.
At 10:00 am B and A are separated by 60 km.
The relative speed of B with respect to A = 80  60 = 20 kmph.
(since, A and B are travelling in the same direction)
The time taken by B to meet A = 60/20 = 3 hours.
At 10:00 am + 3 hours = 1:00 pm, B meets A.
3. 

Let the distance be 'd'
Total distance travelled = 2d
Total time taken = (d/30) + (d/90)
Average speed = 2d/{(d/30) + (d/90)} = (2 x 30 x 90)/(30 + 90) = 45 kmph.
4. 

If Q starts from the same point from which P started, then the distance of separation between them is the distance travelled by P in 2 hours, (because 8:00 am  6:00 am = 2 hours).
The information about the starting points of P and Q is not available. Hence, the question cannot be answered.
5. 

Let the actual distance travelled be X km.
Then, X/10 = (X + 20)/14
14X = 10X + 200
4X = 200
X = 50 km
6. 

Total distance travelled by A = 3 x 60 + 4 x 95 = 560 km.
Total time taken = 3 + 4 = 7 hours.
Average speed = 560/7 = 80 kmph.
7. 

Difference in speeds of Suresh and Ganesh is = 12  6 = 6 m/sec.
The difference in number of rounds made = Number of rounds made at 6 m/sec.
i.e. (6 x 3600)/300 = 72.
8. 

As the duration of journey at different speeds is constant, the average speed of the journey is average of the speeds.
i.e. (48 + 52)/2 = 50 kmph.
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