Averages

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1) Average = sum of observations/number of observations. 2) If first half of the distance is covered at A Km/hr and second half of the   distance at B Km/hr, then the average speed for the entire journey is Km/hr. 3) If speed is A Km/hr for the first T hours of the journey and B Km/hr for the next T hours of the journey, then the average speed for the entire journey is Km/hr. 4) If each number in the group is increased by 'x', then average of the group also increases by 'x'. 5) If each number in the group is decreased by 'x', then average of the group also decreases by 'x'. 6) If each number in the group is multiplied by 'x', then average of the group also multiplied by 'x'. 7) If each number in the group is divided by 'x', then average of the group also divided by 'x'.