An average also known as the arithmetic mean is the sum of the given observations divided by the number of observations. For instance, if we have 3 numbers 10, 20 and 30 then the average will be
Average = (10+20+30)/3 = 20
Avg = Sum of given observations
Number of observations
If a car or a train travels D distance in T time then the average speed of the car or the train is S.
Average speed S = Distance D
If a car travels from point A to point B at a speed of X kph (kilometer per hour) and travels from point B to point A at a speed of Y kph. Then average speed of the car during the whole journey is
Avg speed (S) = 2XY
If a man drives his Audi from his house to his Office at a speed of 100 kph and returns back from his office back home at a speed of 60kph taking the same route daily then find the average speed.
Given, X = 100 and Y = 60
Then average speed S = 2XY/(X+Y)
= (2 x 100 x 80)/(100 + 60)
= 16000 / 160
= 100 kph
If a car travels distance D1 at a speed of S1 and travels distance D2 at a speed of S2 then the average speed of the whole journey is calculated in the following manner.
Time taken to cover the first part of the journey T1 = D1/S1
Time taken to cover the second part of the journey T2 = D2/S2
Therefore, average speed S = D1 + D2
T1 + T2
If a car travels 100 km at a speed of 50 kph and the next 80 km at a speed of 40 kph then find the average speed of the whole journey
D1 = 100km and S1 = 50kph
D2 = 80 km and S2 = 40kph
Time taken to cover first part of the journey T1 = D1/S1 = 100/50 = 2 hours.
Time taken to cover second part of the journey T2 = D2/S2 = 80/40 = 2 hours.
Therefore, average speed of the car is S = (D1 + D2) / (T1 + T2)
= (100 + 80) / (2 + 2)
= 180 / 4
= 45 kph