# Quantitative Aptitude Important Formulas

 Average - Important Formulas,Tricks and Examples Average Average = Sum of quantities/ Number of quantities The average of first n natural numbers is =>[n(n+1)/2] /n => (n +1)/2 Suppose a man covers a certain distance at x kmph and an equal distance at y kmph. Then, the average speed during the whole journey is = 2xy/(x + y) kmph. Mean, Median, Mode, and Range Mean :To find the mean, add all the numbers together then divide by the number of numbers. The mean is not always a whole number. Example: Data Set = 2, 5, 9, 7, 5, 4, 3 Number of Elements in Data Set = 7 Mean = ( 2 + 5 + 9 + 7 + 5 + 4 + 3 ) / 7 = 5 Median :To find the median, order the numbers and see which one is in the middle of the list. If there are two middle values the median is halfway between them. This might not be a whole number. Example: Odd Number of Elements Data Set = 2, 5, 9, 7, 5, 4, 3 Reordered = 2, 3, 4, 5, 5, 7, 9 - the middle term is 5 Median = 5 Data Set = 2, 5, 9, 3, 5, 4 Reordered = 2, 3, 4, 5, 5, 9 - the middle terms are 4 and 5 Median = ( 4 + 5 ) / 2 = 4.5 - the median is the average of the two middle terms Mode :To find the mode, order the numbers lowest to highest and see which number appears the most often. Example: One Mode Data Set = 2, 5, 9, 7, 5, 4, 3 Mode = 5 Range :To find the range, subtract the lowest number from the biggest number. Example: Data Set = 2, 5, 9, 7, 5, 4, 3 Reordered = 2, 3, 4, 5, 5, 7, 9 Range = ( 9 - 2 ) = 7