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What is the original average weight of the class?
In a class, with a certain number of students, if another student, weighing 50 Kg joins, then the average weight of class increased by 1. If one more student weighing 50 Kg joins then the average weight of class increased by 1.5 over the original average.
1. 46
B. 4
C. 2
D. 47



This question is part of Averages Level 1
Asked by Wyatt Williams, Last updated: May 25, 2020

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2 Answers

M. Porter

Here to relax my mind a bit

M. Porter, Senior Executive, Master of Art, San Jose

Answered Mar 28, 2019

The correct answer to this question is D, 47. This questions has to do with averages.In relation to mathematics, an average is defined as a calculated central value of a set of numbers (in this example it is the entire weight of the class). Here is the math equation: let number of students in the class be n

Average weight of the class is x

Total weight of the class = nx

If one student (50 kg) joins, comparing total weight of the class, illustrated as

(n+1)(x+1) = nx + 50

If second student (50 kg) joins, comparing total weight of the class, then:

(n+2)(x+1.5) = nx + 100

Solve:

n + x = 49 - (1)

1.5n + 2x = 97 - (2)

From (1), n = 49 - x

Putting in (2) we get

73.5 + 0.5 x = 97

Thus we get 47: 0.5x = 23.5 or x = 47

 

John Smith

John Smith

Answered Oct 26, 2016

47
 

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