Math, asked by luckyllaher2973, 11 months ago

In a class a boy of marks 60 was replaced by another boy of marks 80 and the average of the class is increased by one mark.Find the strength of the class

nrj017: new student have 20 more marks than previous student. as mentioned in question average is increase by 1 mark. so if those extra 20 marks are distributed to 20 student the average is increased by 1 mark. so answer is 20

Answers

Answered by soumya2301

Mean = sigma x / n

Let the number of students be n

Average = sigma x / n = a (lets say)

sigma x = n×a

corrected sigma x = na-60+80

corrected sigma x = na+20

New average = a+1

corrected sigma x / n = a+1

na+20/n = a+1

na+20 = n(a+1)

na+20 = na + n

n = 20

vaishnavi5570: see let average marks before replacement be x then let z be total marks scored by class except the one who is to be replaced nd y be strenght of the class......... so by this we get x=z+60÷y this is our first equation similarly as per given in question we can make next equation as follows x+1=z+80/y now solve both these equation we get value of y as 20 nd as at first we considerd y as strength of class therefore strenght should be 29

vaishnavi5570: sry 20

saima810: 20

suraj5228: is it 40

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