In a class, there are 20 students whose average age is decreased by two months, when one student aged 18 years is replaced by a new student, find the age of the new student ?
Solution : Age of new student = Age of removed student - Numbers of students * Decrease in average age
= 18 - 20 * ( 2 / 12 ) = 44 / 3 = 14 years 8 monthsRule : If a person travels a distance at a speed of x km/hr, and the same distance at a speed of y km /hr, then the average speed during the whole journey is given by :
Rule : If a person travels three equal distances at a speed of x km / hr, y km / hr and z km / hr respectively. Then the average speed during the whole journey is :
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