The average weight of 15 students in a class is increased by 1.5 kg when one of the students weighing 40 kg is replaced by a new student. find the weight of the new student.
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In average type questions,to find the weight of the new person entered there is a shortcut method.
New Entry weight = New average + (Number of pupil present before the new entry* increase in the average) -->eqn(1)
In the question given weight of the new one=48
New average=41
Given increase in the average is by 1
Substituting these in the above equation(1),
48=41+(no. of persons present)*1
48-41=no. of persons present.
No. of persons present=7
Note: If in the question its given that the new average is decreased when new one is entered then the equation is as,
New entry weight=New average-(number of pupil before the new entry *decrease in the average).
New Entry weight = New average + (Number of pupil present before the new entry* increase in the average) -->eqn(1)
In the question given weight of the new one=48
New average=41
Given increase in the average is by 1
Substituting these in the above equation(1),
48=41+(no. of persons present)*1
48-41=no. of persons present.
No. of persons present=7
Note: If in the question its given that the new average is decreased when new one is entered then the equation is as,
New entry weight=New average-(number of pupil before the new entry *decrease in the average).
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