Question
The average weight of 20 students in a class is 55 kg.
If the weight of the class teacher is included, the average is increased by 0.5 kg. The weight of the class teacher is:Solution
Let the weight of the teacher be 'x' kg. (Sum of total observations) = average × (Total number of observation) Total weight of all students = 55 x 20 = 1100 kg New average = 55 + 0.5 = 55.5 New observation when teacher included = 20 + 1 = 21 So, Total weight of all = 21 x 55.5 =1165.5 kg The weight of the teacher = (Total weight of all) - (Total weight of all students) The required weight = 1165.5-1100 = 65.5kg
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