(c) Let x and y be the upper and lower class limit of frequency distribution. Given, width of the class = 5 ⇒ x-y= 5 …(i) Also, given lower class (y) = 10 On putting y = 10 in Eq. (i), we get x – 10= 5 ⇒ x = 15 So, the upper class limit of the lowest class is 15. Hence, the upper class limit of the highest class =(Number of continuous classes x Class width + Lower class limit of the lowest class) = 5 x 5+10 = 25+10=35 Hence,’the upper class limit of the highest class is 35. Alternate Method After finding the upper class limit of the lowest class, the five continuous classes in a frequency distribution with width 5 are 10-15,15-20, 20-25, 25-30 and 30-35. Thus, the highest class is 30-35, Hence, the upper limit of this class is 35.